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32 Cards in this Set

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Describe the medical utility of the following methods:
1. Northern blotting
2. Southern blotting
3. Western blotting
4. Southwestern blotting
1. Detects RNA with hybridized probe to determine whether gene(s) is/are expressed in cells or tissues
2. Detects DNA sequences with hybridized probe; used to test genetic relatedness or mutation analysis
3. Detects presence of proteins in tissue extract with anti-protein antibodies
4. Detects DNA-binding proteins with oligonucleotide probes; may be used to identify transcription factors
What is the function of carnitine?
Carnitine is a methylated derivative of lysine. It is used by the enzyme carnitine palmitoyltransferase, which transfers a long-chain fatty acyl group from CoA to carnitine. The fatty acid attached to carnitine may then be carried across the inner mitochondrial membrane and into the mitochondrial matrix.
What is the source of physiologic carnitine? In what setting can carnitine deficiency result?
Carnitine is obtained in the diet but primarily comes from endogenous synthesis. Deficiency can result from increased demand (e.g. ketosis) + dietary inadequacy, or from defects in the carnitine metabolic pathways.
What are the clinical features of carnitine deficiency?
Carnitine deficiency may cause hypoglycemia, hyperammonemia, fatty liver, lipid storage myopathy, myoglobinuria, and confusion.
What protein targets misfolded proteins to proteasomes?
ubiquitin
Name the three enzymes that catalyze the three irreversible steps of glycolysis.
hexokinase (glucokinase in liver)
phosphofructokinase-1
pyruvate kinase
Pyruvate carboxylase catalyzes the first irreversible step of gluconeogenesis. What cofactor is required for pyruvate carboxylase function?
biotin
Name the enzyme deficient in von Gierke disease. What are the clinical features of this disease?
glucose-6-phosphatase

Patients with von Gierke glycogen storage disease (abnormal glycogen accumulation in liver and kidney) typically present between 3-4 months of age with hypoglycemia, hyperlipidemia, and lactic acidosis.
Name the enzyme deficient in McArdle disease. What are the clinical features of this disease?
muscle phosphorylase

Patients with McArdle glycogen storage disease have muscle weakness during initial exercise beginning in the second or third decade of life. Rhabdomyolysis and myoglobinuria are possible.
Name the enzyme deficient in Hurler syndrome. What are the clinical features of this syndrome?
alpha-L-iduronidase

Hurler syndrome is a lysosomal storage disease. Patients present with hepatosplenomegaly, dwarfism, skeletal abnormalities, mental retardation, and corneal clouding.
Name the enzyme deficient in Gaucher disease. What are the clinical features of this disease?
beta-glucocerebrosidase

Gaucher disease is a lysosomal storage disease. It is characterized by hepatosplenomegaly and glucocerebrosidase accumulation in phagocytic cells.
What is the mechanism of anemia in pyruvate kinase deficiency?
Pyruvate kinase deficiency is an autosomal recessive condition that leads to a hemolytic anemia. Pyruvate kinase catalyzes conversion of PEP to pyruvate in glycolysis. In PK deficiency, red cells cannot produce sufficient ATP to power the membrane-bound Na+/K+ pump, leading to cell swelling and lysis.
Describe the clinical significance of ornithine transcarbamylase (OTC) deficiency.
OTC deficiency leads to decreased elimination of ammonia, causing hyperammonemia. This can result in coma, brain damage, and death. OTC deficiency often becomes apparent in the first few days of life.
What is the enzyme deficiency in albinism?
The most common form of albinism is due to deficiency of coppper-dependent tyrosine hydroxylase, which results in non-production of melanin from the aromatic amino acid tyrosine.
Name the enzyme deficient in Tay-Sachs disease. What are the clinical features of this disease?
hexosaminidase A

In Tay-Sachs disease, a deficiency of hexosaminidase A leads to accumulation of ganglioside GM2 in neurons. This leads to blindless, loss of developmental milestones, and death before age 5.
What are the clinical manifestations of debranching enzyme deficiency?
Debranching enzyme deficiency is characterized by mild fasting hypoglycemia and hepatomegaly.
What are the clinical manifestations of glucose-6-phosphatase deficiency?
Defects in or deficiency of glucose-6-phosphatase leads to profound fasting hypoglycemia, lactic acidosis, hepatomegaly, hypertriglyceridemia, and hyperuricemia.
What is the rate-limiting step in catecholamine synthesis?
The rate-limiting step in catecholamine synthesis is conversion of tyrosine to L-dihydroxyphenylalanine (L-dopa) by tyrosine hydroxylase. Dopa decarboxylase then converts dopa to dopamine. As dopamine passes through the vesicle membrane, dopamine beta-hydroxylase converts it to norepinephrine, which is stored in the vesicle.
What enzyme converts norepinephrine to epinephrine?
Phenylethanolamine-N-methyltransferase (PNMT)

In periods of stress, cortisol release stimulates expression of PNMT gene.
What enzymes important in heme synthesis are inhibited by lead poisoning?
aminolevulinate (ALA) dehydratase
ferrochelatase (heme synthase)
What are the presenting symptoms of lead poisoning?
lethargy
headache
memory loss
nausea
abdominal pain
diarrhea or constipation
What are the hematologic findings in lead poisoning?
Lead poisoning leads to a microcytic, hypochromic anemia due to impaired heme synthesis. Lead also inhibits 5' nucleotidase activity, producing basophilic stippling of erythrocytes due to retained RNA.
What is the treatment of lead poisoning?
In lead toxicity with encephalopathy: dimercaprol (crosses blood-brain barrier). Chelation therapy with ethylenediaminetetraacetic acid (EDTA) is indicated for high blood lead levels.
Give the locations of the following enzymes:
1. Carnitine acyltransferase II
2. Fatty acyl CoA synthetase
3. Glucose-6-phosphate dehydrogenase
4. Hexokinase
5. Pyruvate kinase
6. TCA cycle enzymes
1. Carnitine acyltransferase II: inner mitochondrial membrane
2. Fatty acyl CoA synthetase: outer mitochondrial membrane
3. Glucose-6-phosphate dehydrogenase: cytosol
4. Hexokinase: cytosol
5. Pyruvate kinase: cytosol
6. TCA cycle enzymes: mitochondrial matrix (except succinate dehydrogenase)
For each of the following compounds, give the precursor amino acid:
1. nitric oxide
2. gamma-amino butyric acid (GABA)
3. Melatonin
4. Melanin
5. Serotonin
6. Thyroid hormones
7. Dopamine, norepinephrine, epinephrine
1. nitric oxide: arginine
2. gamma-amino butyric acid (GABA): glutamate
3. Melatonin: tryptophan
4. Melanin: tyrosine
5. Serotonin: tryptophan
6. Thyroid hormones: tyrosine
7. Dopamine, norepinephrine, epinephrine: tyrosine
What is the enzyme deficiency in I-cell disease?
N-acetylglucosamine-1-phosphotransferase, an enyzme essential for targeting lysosomal enzymes from the Golgi apparatus to lysosomes
What are the consequences of galactokinase deficiency?
Galactokinase catalyzes the phosphorylation of galactose; deficient individuals experience accumulation of galactose in peripheral blood. Several tissues (including the lens of the eye) contain aldose reductase, which converts galactose to galactitol. Accumulation of galactitol in the lens causes osmotic damage and leads to cataracts.
What are the consequences of fructokinase deficiency?
Fructokinase deficiency generally has no clinical manifestations; it is often discovered as an incidental finding of fructose in the urine
What are the consequences of galactose-1-phosphate uridyltransferase deficiency?
Deficiency of galactose-1-phosphate uridyltransferase results in galactosemia. Patients are unable to metabolize galactose-1-phosphate, which accumulates in kidneys, liver, and brain. Infants with this condition often present with jaundice, cataracts, and failure to thrive.
What are the consequences of fructose-1,6-bisphosphate aldolase deficiency?
Fructose-1,6-bisphosphate aldolase catalyzes the hydrolysis of fructose-1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde phosphate. Upon ingestion of fructose, deficient patients experience rapid accumulation of fructose-1-phosphate in the kidneys, liver, and intestine, leading to toxic damage of these tissues.
What is the enzyme deficiency in maple syrup urine disease? What amino acids should be minimized in the diets of patients with this disease?
branched-chain ketoacid dehydrogenase

Leucine, isoleucine, and valine should be minimized in the diet.
What protein is defective in osteogenesis imperfecta? What amino acids are critical to the synthesis of this protein?
type I collagen

glycine, proline