enzymes 1 Flashcards Preview

biochem block 1 > enzymes 1 > Flashcards

Flashcards in enzymes 1 Deck (24):
1

describe the unusual temperature dependence of enzymes

initially, increasing temp will increase rate (2x per 10*C) until temp is too high and enzyme begins to denature, then enzyme activity will decrease

2

discuss the significance of G6P dehydrogenase mutation

enzyme is impt in RBC membrane, d/t the mutation of G6PD, less NADPH is formed and bc less NADPH is formed, there is less to participate in the reduction of glutathione, leading to less GSH. when GSH levels are low, peroxides and free radicals accumulate, leading to cell damage

3

which aa form covalent intermediates? (4)

cysteine
lysine
serine
histidine

4

which aa participate in acid-base catalysis? (2)

histidine
aspartate

5

which aa stabilize anions? (3)

peptide backbone-NH
arginine-NH
serine-OH

6

which aa stabilize cations? (1)

aspartate- COO-

7

function of lyases

add/remove groups to form double bonds

8

vitamin B1

thyamine pyrophosphate
-aldehyde transfer
- beri-beri if deficient
used by pyruvate dehydrogenase

9

vitamin B2

riboflavin (FAD)
- Redox
- chellosis, dermatitis

10

vitamin B6

pyridoxal phosphate
- group transfer to and from aa
- depression, confusion if deficient
used in liver to keep toxic NH2 from accumulating in the blood

11

nicotinic acid

NAD
-Redox
- pellagra (dermatitis, depression, diarrhea) if deficient

12

biotin

activates and transfers CO2

13

coenzyme A

used to transfer acyl groups or thiol esters

14

cofactor used by alcohol dehydrogenase

NAD

15

in the active site of alcohol dehydrogenase (3)

Zn, serine and histidine

16

stereospecificity of alcohol dehydrogenase

enzyme is steroespecific in that H and D forms are not equal

17

catalysis and motion

enzymes help to catalyze run by restricting motion, the more restricted the motion, the faster the rate of rxn

18

4 aa found in the active site of all of the serine proteases

serine
histidine
glycine
asparagine

19

which other enzyme has identical catalytic site to serine proteases?

acetylcholinesterase

20

MOA of chymotrypsin (9)

-substrate binds to substrate-specificity site
- His activates Ser for nucleophilic attack
-Ser attacks at carbonyl carbon and oxyanion tetrahedral intermediate is formed between Ser, Gly and substrate
-peptide bond is cleaved, amino portion released
-covalent act-intermediate between Ser and substrate
- hydrolysis
- formation of second oxyanion intermediate
- acid-base catalysis with histidine breaks acyl-enzyme bond
- product dissociates

21

different binding sites for the serine proteases (3)

chymotrypsin- open for large, hydrophobic substrates
trypsin- has aspartate in site (-), so attracts (+) substrate
elastin- has valine and threonine blocking binding site, only allows small substrates like glycine

22

enzyme that activates trypsinogen --> trypsin

enteropeptidase

23

3 enzymes activated by trypsin

proelastase --> elastase
procarboxypeptidase --> carboxypeptidase
chymotrypsin --> p-chymotrypsin

24

what causes the formation of a-chymotrypsin?

p-chymotrypsin (both forms are active)