Enzymes

Question 1

Enzyme nomenclature

Answer 1

1. Oxidoreductases: catalyze oxidation-reduction reactions such as Lactate dehydrogenase
2. Transferases: catalyze transfer of C-, N-, or P- containing groups.
3. Hydrolases: catalyze cleavage of bonds by addition of water.
4. Lyases: catalyze cleavage of C-C, C-S, and certain C-N bonds.
5. Isomerases: catallyze racemization of optical or geometric isomers; rearranging stereoisomers require breaking of bonds
6. Ligases: catalyze formation of bonds between carbon and O, S, N, coupled to hydrolysis of high-energy phosphatates, such as: Pyruvate carboxylase (pyruvate → oxaloacetate)

Question 2

Irreversible inhibitors

Answer 2

1. DIPF - a neurotoxin
2. Penicillin - irreversibly inhibits the bacterial transpeptidase (peptidoglycan cell wall)
3. Heavy metals - tightly bind thiols (SH) in enzymes

Question 3

Additional Enzyme Inhibitors

Answer 3

1. Allopurinol - targets Xanthine oxidase; drug for treatment of gout
2. B-Aminopropionitrile - targets Lysyl oxidase; causes abnormal collagen cross-linking (lathyrism); toxin
3. 5-Fluorouracil - targets Thymidylate synthetase; anticancer drug
4. Methotrexate - targets Dihydroffolate reductase (folate = vitamin); Cancer chemotherapy.
5. Acyclovir - targets DNA Polymerase; Anti-viral drug (herpes)
6. Sildenafil (Viagra) - targets Phosphodiesterase type 5; treatment of erectile disfunction
7. Reverse Transcriptase Inhibitors - targets reverse transcriptase; treatment of retroviruses (HIV)

Question 4

Therapeutic enzymes

Answer 4

1. Streptokinase - pulmonary embolism, myocardial infarction
2. Tissue plasminogen activator - pulmonary embolism, myocardial infarction
3. Pancreatic enzymes - replacement for pancreatic enzymes
4. L-asparaginase - treatment for leukemia
5. Lactase - digestion of lactose
6. Biotene - oral hygiene; treatment for xerostoma (dry mouth).

Question 5

Catalytic efficiency

Answer 5

1. Acid-base catalysis
2. Covalent catalysis
3. Catalysis by proximity
4. Catalysis by strain