23 terms

USMLE Biochem Enzymes

Top USMLE Enzymes from Kaplan Biochem

Terms in this set (...)

HMG-CoA Reductase
a. HMG-Coa --> mevalonic acid
b. Inhibited by statins (competitive inhibitors) increase km nothing to vmax
c. Upregulate LDL receptors
d. Steroid Hormones vit D and bile salts are made from cholesterol (7 hydroxylase)
a. Important enzyme in the PPP cycle
b. NADPH, Ribose 5-phosphate
c. Glut peroxidase/glut reductase
d. NADPH Oxidase def -chronic granulomatous disease
e. Heinz bodies present in blood
f. Fava bean or antimalarials -->hemolytic crisis
Methylmalonyl CoA Mutase
a. Vit B 12 required by this enzyme
b. Important for metabolism of odd numbered fatty acids
c. ABCs of carboxylase ATP, Biotin, CO2
d. Propionyl Coa --> Methylmalonyl CoA --> Succinyl CoA
UDP glucoronyl transferase
a. Responsible for conjugating bilirubin in your liver
b. Gilgert Syndrome- minor defect in enzyme --> minor hyperbilirubinemia
c. Crigler-Najjar - major defect --> severe hyperbilirubinemia
d. Unconjugated indirect bilirubin build up in the system
Homocysteine Methyltransferase (methionine synthase)
a. Folate, B12 are required by this enzyme
b. Responsible for conversion in the homocysteine --> methionine
c. If you give folate to B12 deficient patient it will correct megaloblastic anemia but not the peripheral neuropathy
Dihydrofolate Reductase
a. Folate --> dihydrofolate --> tetrahydrofolate
b. Blocked by methotrexate, trimethoprim, sulfamethoxazole. pyramethamine
Thymidylate Synthase
a. dUMP --> dTMP
b. inhibited by 5-flouro uracil (5-FU)
c. give lucovorine with 5 FU, helps rescue the folic acid?
a. Lesch Nyhan - X linked --> high uric acid levels (build-up of Monosodium Urate crystals & self-mutilation)
b. Purine salvage pathway
Branched Chain Ketoacid Dehydrogenase
a. Maple syrup urine disease (MSUD)
b. Isoleucine, leucine, and valine (branched chain amino acids)
c. Presentation: hyperketosis, hypotonia, developmental problems, lethality
Gamma glutamyl carboxylase
a. Vit K dependent enzyme (clotting Factors 2, 7, 9, 10, protein C and S)
Epoxide reductase
a. Inhibited by Warfarin
b. Necessary to recycle Vit K --> decrease in clotting factors
Xanthine oxidase
a. Inhibited by Allopurinol
b. Xanthine --> Uric acid
c. Gout - negative birefiringence needles shaped crystals
Hexosiminidase A
a. Def. --> increased ganglioside m 2
b. Tay sachs
Galactose 1-P- Urydil Transferase
a. Builds up causes phosphorylated intermediate --> cataracts, GI symptoms, Hepatospenomegaly, Brain problems
Aldose Reductase
a. Galactitol
b. Glucose --> Sorbitol
Adenosine Deaminase
a. Autisomal recessive Severe combined immunodeficiency
b. X- linked SCID - defect in IL2 gamma chain
Acetyl CoA Carboxylase
a. Regulatory enzyme of Fatty Acid synthesis
b. Feed forward stimulation - citrate turns it on
c. Feed back inhibition - palmatyl Coa turn off
d. Insulin stimulate through - dephosphorylation
e. Glucagon inactivate -through phosphorylation
a. Directly stimulated through insulin makes Fructose 2, 6 bisphosphate which stimulates PFK 1
PDH [pyruvate dehydrogenase]
A) First component enzyme of pyruvate dehydrogenase complex (PDC).
B) Contributes to transforming pyruvate into acetyl-CoA via pyruvate decarboxylation.
C) Acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration, so pyruvate dehydrogenase contributes to linking the glycolysis metabolic pathway to the citric acid cycle and releasing energy via NADH.
Hormone sensitive lipase
a. Sensitive to a drop in insulin at the level of adipose
b. When active breaks down triglyceride in adipose tissue into fatty acids and glycerol and released into blood stream
Lipoprotein lipase
a. Activated by Apo CII on chylomicron and VLDL particles
b. Apo CII interacts with particles and taken up into tissues
Iduronidate Sulfatase/iduronidase
a. Defect in iduronidate sulfates --> hunters disease (X-linked) [hunter aims for an X}
b. Iduronidase def. --> hurlers disease (corneal clouding) Autosomal [hurlers don't need to see they just hurl things]
c. Both present with gargoyle facies, problems in cerebral development, fatal (but hurlers have corneal clouding)
ALA dehydratase/Ferrocheletase
a. Enzymes inhibited by lead