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74 Cards in this Set

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G6PDH

Reactant and product
Reactant: Glucose-6-P

Product: 6-phosphogluconate
G6PDH

cofactor
NADP

(rxn: NADP ---> NADPH)
G6PDH

part of what pathway?
Hexose monophosphate shunt
G6PDH

induced by
insulin
G6PDH

activated by
NADP (decrease in NADPH/NADP ratio)
G6PDH deficiency

inheritence
XLR
G6PDH

major function
Generate NADPH for anabolic purposes (EG: FA synthesis), antimicrobial killing and protection of cells from reactive oxygen species
Describe the role of NADPH in protecting against ROS (particularly in RBCs)
NADPH reduces oxidized Glutathionine (G-S-S-G) back to its reduced form (2 GSH). GSH allows the enzyme Glutathionine peroxidase to breakdown H202
G6PDH deficiency

3 key features
-immunodeficiency (in severe disease)

- Heinz bodies

-hemolytic anemia
G6PDH deficiency

stressors that can acute hemolytic anemia
-ifn

-drugs (sulfas, chloroquine)

-fava beans
G6PDH deficiency

Why can this condition lead to immunodeficiency?
NAPDH oxidase generates bactericidal superoxide. NADPH deficiency inhibits this function.
CGD/NADPH deficiency

How can the diagnosis be confirmed
a NEGATIVE nitroblue tetrazolium test
HMG CoA reductase

location
ER
HMG CoA reductase

activated by?
insulin
HMG CoA reductase


enzyme ACTIVITY is inhibited by
-glucagon

-statins
HMG CoA reductase
reaction
HMG-CoA is converted to mevalonate
HMG CoA reductase

cholesterol effect on the enzyme
Increased hepatic cholesterol represses expression and enhances degradation
HMG CoA reductase

How does inhibition by statin drugs decrease cholesterol levels?
Inhibition by statins both decreases de novo synthesis and enhances hepatic clearence of serum cholesterol by increased LDLR expression
HMG CoA reductase

statins are _________ inhibitors
competitive
DHFR

reaction it catalyzes
Folate---->DHF--->THF
DHFR

eukaryotic inhibitior
methotrexate
DHFR

prokaryotic inhibitors (2)
-Trimethoprim

-pyrimethamine
DHFR

Most important downstream consequence of inhibition?
A block of DHFR function ultimately prevent synthesis of thymidylate (thymidylate synthase is folate dependent)
how can ornithine transcarbamylase deficiency be distinguished from orotic aciduria
OTCD has hyperammonia and low BUN

Orotic aciduria has a normal BUN
Orotic Aciduria

enzymatic causes
- orotic acid phosphoribosyltransferase deficiency

OR

- OMP decarboxylase deficiency
UDP-Glucuronyl transferase

key reaction
Bilirubin + glucoronide ----> bilirubin-diglucoronide
UDP-Glucuronyl transferase

significance in neonates
UDP-Glucuronyl transferase is the last enzyme expressed in infants. Thus, neonates have increased susceptibility to jaundice and kernicterus
Dubin-Johnson syndrome

characterized by
black pigment in the liver due to impaired excretion of direct bilirubin
Crigler-Najjar syndrome

define
a severe UDP-Glucuronyl transferase deficiency
Gilbert Syndrome

define
a benign UDP-Glucuronyl transferase deficiency
gamma-glutamyl carboxylase

rxn:
glu -----> gamma gultamic acid
gamma-glutamyl carboxylase

function and substrate of this rxn:
gamma carboxylation of factors II, VII, IX, X and Protein C&S generates Ca binding sites.
gamma-glutamyl carboxylase

dependent on?
vit K
gamma-glutamyl carboxylase

inhibited by
warfarin and dicoumarol
Warfarin

does this drug inhibit in vitro clotting?
NO, warfarin's effect (vit K reductase inhibition) prvents in vivo clotting by blocking clotting factor synthesis but has no effect on existant factors.
gamma-glutamyl carboxylase

this reaction catalyzes what type of modification
cotranslational modification of clotting factors
Homocysteine methyltranferase

rxn:
homocysteine ---> methionine
Homocysteine methyltranferase

cofactors:
-N5-methyl THF

-methylcobalamin (B12)
mild homocysteinuria is associated with deficiencies is what vitamins
folate
B12
B6 (cystathionine synthase rxn)
mild homocysteinuria

symptoms
-DVT
-stroke
-atherosclerosis
how can B12 deficiency be distinguished from folate deficiency?
B12 deficiency is associated with methylmalonic aciduria
name the 3 "ABC" carboxylases
(ATP, Biotin, Co2)

-propionyl-CoA carboxylase
-acetyl-CoA carboxylase
-pyruvate carboxylase
Methylmalonyl-CoA mutase

rxn:
Methylmalonyl-CoA ---> succinyl-CoA
Methylmalonyl-CoA mutase

cofactor:
adeonsylcobalamin (B12)
Methylmalonyl-CoA mutase

deficiency results in:
Methylmalonylic aciduria and peripheral neuropathy
Lesch-Nyhan Syndrome

inheritence:
XLR
Lesch-Nyhan Syndrome

genetic cause:
HGPRT deficiency
Lesch-Nyhan Syndrome

symptoms:
-spastic cerebral palsy
-self-mutilation
-hyperuricemia
-early death
6-Mercaptopurine is activated by
HGPRT
Lesch-Nyhan Syndrome

pathophysiology
Loss of the salvage pathways results in shunting of Hypoxanthine and guanine to the excretion pathway.

Furthermore, loss of feedback inhibition of PRPP admidotransferase results in additional purine synthesis.

Thus, HGPRT deficiency leads to crippling excesses of urate
HGRPT

rxn:
hypoxanthine/guanine -----> IMP/GMP
Branched-chain Ketoacid DH

cofactors:
TPP
Lipoic acid
CoA
FAD
NAD
Branched-chain Ketoacid DH

critical in the metabolism of
Valine
Leucine
Isoleucine
Branched-chain Ketoacid DH

associated disease:
maple serup urine disease
maple serup urine disease

symptoms:
-urine has a maple odor
-mental retardation
-abnormal muscle tone
-ketosis
-coma,death
name the substances that enter the propionyl-CoA pathway
(VOMIT)

Valine
Odd chain FA
Methionine
Isoleucine
Threonine
Pyruvate DH

cofactors
TPP
Lipoic Acid
CoA
FAD
NAD
Pyruvate DH

rxn:
pyruvate------> acetyl CoA
Pyruvate DH

deficient in what population (consequence)
alcoholics due to thiamine deficiency (results in lactic acidosis)
Pyruvate DH

inhibited by
acetyl-CoA
PKU

genetic causes
phenylalanine hyxdroxylase deficiency

OR

tetrahydrobiopterin deficiency
Aspartame is contraindicated in what condition
PKU
PKU

untreated symptoms
-pale skin and white hair

-mental retardation

-loss of motor control

-musty, mousy odor
PKU

-pathophysiology
elevated phenylalanine has a neurotoxic effect
Phenylalanine hydroxylase

rxn
phe ---> tyrosine
MCAD

function
oxidation of medium chain FA
MCAD deficiency

symptoms
-fasting hypoglycemia
- NO KETONES
-C8-10 acyl carnitines in blood
-DICARBOXYLIC ACIDEMIA
Dicarboxylic acidemia is pathognomonic for
MCAD deficiency
Topoisomerase II

inhibited by what drug class in prokaryotes
-quinolones
Topoisomerase II
function
relieves positive supercoiling during DNA replication by introducing negative supercoils
Topoisomerase II

target for what drugs in eukaryotes
etoposide
teniposide
Excision endonuclease

function
removal of intrastrand thymine dimers
Xerderma pigmentosum

defective gene
excision endonuclease
Xerderma pigmentosum

symptoms
extreme UV sensitivity
excessive freckling
multiple skin cancers
corneal ulcerations