Biochemistry Fa

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Rate limiting enzyme for glycolysis

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Phosphofructokinase-1 PFK-1

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Rate limiting enzyme for gluconeogenesis

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Fructose-1,6-bisphosphatase

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Rate limiting enzyme for TCA cycle

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Isocitrate dehydrogenase

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Rate limiting enzyme for Glycogen synthesis

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Glycogen synthase

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Rate limiting enzyme for glycogenolysis

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Glycogen phosphorylase

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Rate limiting enzyme for HMP shunt

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G6PD

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Rate lmiting step for de novo pyrimidine synthesis

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Carbamoyl phosphate synthetase II

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RL enzyme for de novo purine synthesisi

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Glutamine-PRPP-amidotransferase

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RL enzyme for urea cycle

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CPSI

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RL enzyme for FA synthesisi

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Acetyl-CoA carboxylase (ACC)

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RL enzyme for FA oxidation

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Carnitine acyltransferase I

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RL enzyme for ketogenesis

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HMG-CoA synthase

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RL enzyme for cholesterol synthesis

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HMG-CoA reductase

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Defiency of Glucose-6-phosphatase --> severe fasting hypoglycemia, inc in glycogen in liver, increase blood lactate, hepatomegaly

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Von Gierke's (Type I)

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Deficiency of lysosomal alpha-1,4-glucosidase --> cardiomegaly & systemic findings leading to early death

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Pompe's Disease (Type II)
- Pompe's trashes Pump --(Heart, liver, muscle)

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Defiency of debranching enzyme (alpha-1,6-glucosidase) --> Milder form type I w/ normal blood lactate levels. Gluconeogenesis is still intact

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Cori's disease (type III)

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Defiency in skeletal muscle glycogen phosphorylase --> Increase glycogen in muscle but cannot break it down, leading to painful muscle cramps, myoglobinuria with stenuous exercise.

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McArdle's diseae (type V)

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What are the five cofactors for the pyruvate dehydrogenase complex?

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TLC For Noone
TPP - pyrophosphate (Thiamine B1)
Lipoic acid
CoA (B5, pantothenate)
FAD (B2, riboflavin)
NAD (B3, niacin)

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What other enzyme is the pyruvate dehydrogenase compound similar to ? --> same cofactors, substrate & action

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alpha-ketogluterate

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What inhibits lipoic acid and what are the findings?

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Arsenic - vomiting, rice water stools, garlic breath

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What are your ketogenic aa

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Leucine & Lysine

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What does pyruvate dehydrogenase complex defiency result in?

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Lactic acidosis --> Neuro defects due to backup of substrates pyruvate & alanine

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Defiency of Glucose-6-Phosphatase--> severe fasting hypoglycemia, increase glycogen in liver, increase blood-lactate, hepatomegaly

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Von Gierke's Disease (type I) -glycogen storage disease. Body can't maintaing normal blood sugar levels, liver can't get rid of glycogen --> hepatomegaly & increased glycogen stores

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Defiency of lysosomal alpha-1,4-glucosidase (acid maltase) --> cardiomegaly & systemic findings leading to early death

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Pompe's Disease (type II)
Pompe's trashes the Pump --> heart liver, & muscle. Can't break glycogen down in the lysosome

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Defiency of debranching enzyme - alpha-1,6-glucosidase --> milder form of Von Gierke's with normal blood lactate levels. Gluconeogenesis is intact Because still getting glucose-6-phosphate from glucose 1 phosphate via phosphglucomutase

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Cori's Disease (type III)

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ZDefiency in skeletal muscle glycogen phosphorylase --> inc glyocgen in muscle but can't break it down leading to painful muscle cramps, myoglobinuria with strenous exercise

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McArdle's Disease (V)

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Hereditary deficiency of aldolase B. Accumulation of Fructose-1-phosphate --> decreasing available phosphate --> inhibits glycogenolysis & gluconeogenesis
Sx: hypoglycemia, jaundice, cirrhosis, vomiting
Tx: dec intake of both fructose & sucrose

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Fructose intolerance

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Defect in fructokinase. Fructose in blood & urine.

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Essential fructosuria

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Absence of galactose-1-phosphate uridyltransferase. FTT, jaundice, heptomegaly, infantile cataracts, mental retardation

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Classic galactosemia

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Hereditary defiency of galactokinase. Galactitol accumulates (converted to alcohol form via aldolase reductase).

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Galactokinase deficiency

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Ketogenic amino acids

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Leucine, Lysine

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glucogenic amino acids

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Methionine, Valine, Arginine, Histidine

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Glucogenic/ketogenic

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Ile, Phe, Thr, Trp

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Tryptophan makes what substances?

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Niacin --> NAD (B6)
Serotonin (BH4) --> Melatonin

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HIstidine is a precursor to what?

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Histamine (B6)

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Glycine is a precursor to what?

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Porphyrin --> Heme (B6)

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Arginine is a precursor to what?

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Creatinine, Urea, NO

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Glutamate is a precursor to what?

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GABA (B6)
Glutathione

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Phenylalanine is precursor to what substances?

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Tyrosine --> THyroxine & Dopa --> Dopamine & Melanin --> NE --> Epinephrine

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What amino acid becomes essential in PKU?

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Tyrosine (no Phe --> Tyr conversion by phenylalanine hydroxylase)

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Dopa decarboxylase requires what enzyme?

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B6

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What are the phenylketones?

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Phenylacetate, phenyllactate & phenylpyruvate

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What are the findings in PKU?

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Mental retardation, growth retardation, seizures, fair skin, eczema, musty body odor

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Defiency of homogentisic acid oxidase

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Alkaptonuria (ochronosis)

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What are the findings in alkaptonuria? What enzyme is deficient?

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Homogentisic acid oxidase --> Dark CT, pigmented sclera, urine turns black when sits out, debilatating arthralgias (defect in breakdown of tyrosine)

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Congenital albinism is due to defiency of what?

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Tyrosinase (inability to synthesize melanin from tyrosine) (AR) or defective tyrosine transporters (dec amts of tyrosine & thus melanin)
OR can result from lack of migration of neural crest cells

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What are the 3 types of homocystinuria?

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Cystathionine synthase deficiency

Dec affinity of cystathionine synthase for pyridoxal phosphate

Homocystein methyltransferase def

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What are the findings of homocystinuria?

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Inc homocysteine in the urine, MR, osteoporosis, tall stature, kyphosis, lens subluxation (down & inward( & atherosclerosis (stroke & MI)

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How do you treat homocystinuria

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Decrease methionine & increase cysteine in diet & supplement B12 & folate & B6

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What is cystinuria?

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Hereditary defect of renal tubular amino acid transporter for cysteine, ornithine, lysine & arginine in PCT. --> precipitation of cystine kidney stones

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Tx of cystinuria

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Acetazolamide to alkalinize the urine

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What is maple syrup urine disease?

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Blocked degradation obranched amino acids (Ile, Le, Val) due to dec alpha ketoacid dehydrogenase. --> Increase alpha ketoacids in blood. Urine smells like burnt sugar & have dystonia & poor feeding

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What is Hartnup disease?

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AR d/o by defective neutral aa transporter on renal & intestinal epithelial cells. Tryptophan excretion in urine and absorption from gut. Leads to pellagra

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When does gluconeogenesis begin in the postabsorptive period? When does it become fully active?

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Begins 4-6 hours after last meal
Fully active when glycogen stores are depleted (10-18 hrs)

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What is the main energy usage & fuel production in early starvation (24 hours)

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Glucose is produced via glucoengenesis & FA usage from adipose tissue

Brain uses mainly glucose & muscles and other tissues use some glucose but predominantly fatty acids

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In intermediate starvation (48 hrs after last meal) what fuel is produced? Used?

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Produced: Glucose (gluconeogenesis), FA from adipose tissue, ketones from liver

Used: Brain glucose but some ketones; muscles & other tissues use FA but some ketone bodies

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What metabolic scenario favors synthesis of ketones?

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Excess acetyl CoA from fatty acid metabolism

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What does the brain & muscles use in prolonged starvation (5 days after last meal)?

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Brain uses ketones & muscles use fatty acids & some ketones)

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During a 3 day fast what is the percentage of ketone bodies & glucose?

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60% - ketone bodies
40% - glucose (glueneogenesis)

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What lysosomal storage disease is a/w renal failure?

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Fabry's
Tx: dialysis

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What are the only two X-Linked recessive lysosomal storage diseases? What is the method of inheritance of the others?

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X Linked: Fabry's & Hunters (X marks the spot)

The rest are autosomal recessive

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What is the most common lysosomal storage disease?

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Gaucher's

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Which lysosomal storage diseases are a/w an early death (usually by age 3)?

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Tay Sachs
Niemann Pick
Krabbe's

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Which lysosomal storage disease is a demyelinating disease?

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Metachromatic leukodystrophy

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How does corneal clouding & mental retardation help distinguish between the mucopolysaccharidoses?

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Hurlers: corneal clouding & MR

Hunters: no corneal clouding but has MR

Schele's: corneal clouding but no MR

I-Cell: corneal clouding +/- MR

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What glycogen storage disease has alpha-L-iduronidase def?

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Hurlers & Schele's

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What glycogen storage disease has iduronate sulfatase deficiency?

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Hunter's

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What glycogen storage disease has deficiency in arylsulfatase A?>

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Metachromatic leukodystrophy

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What glycogen storage disease has a deficiency in alpha-galactosidase?

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Fabry's

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What glycogen storage disease has a deficiency in galactocerebrosidase (--> galactocerebroside accumulation)

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Krabbe's disease

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What glycogen storage disease has a deficiency in beta-glucocerebrosidase ( --> glucocerebroside accumulation)

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Gauchers ---- Most common glycogen storage disease

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What glycogen storage disease has a deficiency of hexosaminidase?

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Tay-Sachs (taySaX)

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What glycogen storage disease has a deficiency of sphingomyelinase?

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Niemann Picks (Don't PICK your nose with your SPHINGER)

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Characterized by an accumulation of GM2 ganglioside

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Tay Sachs

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Accumulation of dermatin sulfate

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Hurlers, Hunters, Schie's

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Common among Ashkenazi Jews?

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Tay Sachs, Niemann Pick & some forms of gauchers

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Which glycogen storage disease is characterized by crinkled paper cytoplasm

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Gaucher's

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DDx for cherry red spot on retina?

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Tay Sachs, Niemann Picks, Central Retinal a occlusion

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Deficiency in mannose phosphorylation , death by age 8, corneal clouding, coarse facies, HSM, skeletal abnormalities, restricted joint mvmt, +/-

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I Cell Disease

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Name genetic syndrome:
alcoholics --> B1 deficiency --> neuro effects

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Pyruvate dehydrogenase deficiency

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Absence of HGPRTase

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Lesch Nyan

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Deficiency of aldolase B

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Fructose intolerance

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Defective excision repair (endonuclease) --> Thymidine dimer formation

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Xeroderma pigmentosum

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Heinz bodies

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G6PD

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Must/mousy odor, albinism, MR, eczema

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PKU

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Galactose-1-p-uridyltransferase deficiency --> MR, HSM, cataracts

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Classic galactosemia

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Hyperextensible skin, loose joints, bleeding tendency (collagen defect)

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Ehlers Danlos

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Decreased NADPH due to lack of HMP enzyme

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Glucose -6-Phosphate Dehydrogenase deficiency

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Inherited defect in tubular aa transporter

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Cystinuria

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To tx this d/o dec dietary methionine, increased cysteine & B6

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Homocystinuria

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Deficiency of tyrosinase

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Albinism

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must increase dietary tyrosine

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PKU

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Deficiency in homgentisic acid oxidase

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Alkaptonuria

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Hypoglycemia + jaundice + cirrhosis

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Fructose intolerance

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Self mutilation, gout, aggression, choreoathetosis

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Lesch Nyan

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Blacked degradation of branched chain aa

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Maple Syrup urine disease

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Dec fructose & sucrose intake to tx this

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Fructose intolerance

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Inc intake of ketogenic aa

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Pyruvate dehyodrogenase deficiency

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Dark brown urine, organs, & CT; benign disease

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Alkaptonuria

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To tx this d/o dec dietary methionine, increased cysteine & B6

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Homocystinuria

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Deficiency of tyrosinase

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Albinism

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must increase dietary tyrosine

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PKU

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Deficiency in homgentisic acid oxidase

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Alkaptonuria

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Hypoglycemia + jaundice + cirrhosis

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Fructose intolerance

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Self mutilation, gout, aggression, choreoathetosis

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Lesch Nyan

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Blacked degradation of branched chain aa

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Maple Syrup urine disease

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Dec fructose & sucrose intake to tx this

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Fructose intolerance

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Inc intake of ketogenic aa

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Pyruvate dehyodrogenase deficiency

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Dark brown urine, organs, & CT; benign disease

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Alkaptonuria

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To rx this exclude galactose & lactose from diet

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Galactosemia

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what is the activated carrier for CO2

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biotin

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what is the activated carrier for glucose

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UDP glucose

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what is the activated carrier for electrons

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NAD, FAD, NADPH

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Carrier for one carbon units

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Tetrahydrofolate

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Activated carrier for acyl

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CoA & lipoamide

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what cofactor is req'd for all aminotransferases

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B6

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PFK2 increases or decreases levels for F-2,6-BP?

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Increases --> increases glycolysis

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Fructose bisphosphatase 2 is increases or decreases levels for F-2,6-BP?

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Decreases --> increases activity of PKA --> decreases PFK2 --> less glycolysis

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CPS1 is the rate limiting enzyme for what process?

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Urea cycle

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What are the sources of carbon & nitrogen for purines?

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C- THF, glycine, CO2

N-glutamine, aspartate

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Sources of carbon & nitrogen for pyrimidines?

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C- THF, aspartate, CO2

N- glutamine

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Durg inhiits ribonucleotide reductase

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hydroxyurea

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drug inhibits DHFR

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MTX

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drug inhibits IMP dehydrogenase

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mycophenolate

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durg inhibits PRPP synthetase

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6-MP

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Characteristics of orotic aciduria?

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Inability to convert orotic acid to UMP in pyrimidine synthesis --> megaloblastic anemia that does not correct with administration of B12 or folate, no hyperammonemia, FTT & orotic acid in urine

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Sensitivity to ionizing radiation, immunodeficiency, ataxia starting at 1-2 yrs, poor smooth pursuit of eyes may be first sign

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Ataxia telangiectasia

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Mediates reverse transport from periphery to liver. Acts as repository for apoC & apoE (needed for chylomicron & VLDL metab). Secreted from liver & intestine

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HDL

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Delivers hepatic hcolesterol to peripheral tissues. Formed by LPL modification of VLDL in peripheral tissues. Taken up by receptor mediated endocytosis (uses B100)

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LDL

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Formed in degradation of VLDL. Delivers TG's & cholesterol to liver where they are degraded to LDL? What apolipoprotein does it use?

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IDL
B100 & apoE

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Delivers hepatic TG's to peripheral tissues, secreted by liver

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VLDL - uses B100, CII, & apoE

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Delivers dietary TG's to peripheral tissues. Delivers cholesterol to liver in form of chylomicron remnants, which are mostly depleted of triacylglycerols. Secreted by intestinal epithelial cells

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Chylomicrons - uses B48, A-IV, CII, & apoE

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Lipoprotein lipase deficiency or altered apolipoprotein C-II, causes pancreatitis, HSM, & eruptive/purirtic xanthomas (no inc risk for atherosclerosis)

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Type I- hyperchylomicronemias (inc blood levels of TG & cholesterol)

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AD; absent or decreased LDL receptors. Accelerated atherosclerosis, tendon (Achilles) xanthomas & corneal arcus

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IIa- Familial hypoercholesterolemia - increased LDL & elevated blood levels of cholesterol

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Hepatic overproduction of VLDL. Causes pancreatitis

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IV- Hypertriglyceridemia

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What metabolic rxns take place in the mitochondria?

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Fatty acid/beta oxidation, acetyl CoA production, TCA, oxidative phosphorylation

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What metabolic rxns take place in cytoplasm?

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Glycolysis, fatty acid synthesis, HMP shunt, protein synthesis (RER), steroid synthesis (SER)

Front 138

What metabolic rxns take place in both cytoplasm & mitochondria?

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heme synthesis, urea cycle, gluconeogenesis