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Flashcards in Enzymes Deck (31):
1

Ser-proteases

Consist only of proteins (ser=one a.a.)
-Trypsin
-chymotrypsin
-elastase
-acetylcholin esterase

2

Cofactors

Bound to enzymes.
-Metal ions (ion-sulfur clusters, Zn, carbonic anhydrase)

3

Coenzymes

Intermed. carrier of e-, specific atoms or funct.gr.
-Water sol. vit. derivates (NAD+, PALP, TPP)

4

Haloenzyme

Enzyme+coenzyme

5

Apoenzyme

Enzyme-coenzyme

6

Prosthetic groups

Tightly bound organic cofactors
-FAD
-NAD+, NADH+H+

7

Serine proteases

Hydrolyse peptide bonds of proteins
-Chymotrypsin
-Trypsin
-Elastin

8

Major enzymes prod. by pancreas

-Chymotrypsin
-Trypsin
-Elastin

9

Substrate binding site of Chymotrypsin

Ser-189, Gly-216

10

Substrate binding site of Trypsin

Asp-189, Gly-216

11

Substrate binding site of Elastase

Ser-189, Val-216

12

Inhibition of ser-proteases

At Ser-195 by diisopropylphospho-fluoridate DIPF

13

Mechanism of enzyme action

Michaelis-Munten theory
E+S ES E+P

14

Activation energy

Free energy between initial and transitional state

15

Factors affecting enzyme activitiy

-Non-specific: affecting velocity at each enzymatic reaction (temp, pH, denaturation)
-Specific: affecting only certain Es/certain groups of Es (conc. of reactants, inorganic effectors, organic effectors)

16

Michaelis constant - Km

Km is the substrate conc. at which the velocity of the reaction is half the max. value -> the E is saturated in 50% by substrate.

17

Enzyme inhibitors

-Non-specific -> denaturation: acid&bases, temp., alcohol, heavy metals, red. agents
-Specific
1.Irreversible: Ser-proteases, SH-containing E´s (heavy metals), cytochrome oxidase (CN-ions)
2.Reversible: bound to other than S-site
a)Competetive: sim. as S, bound to S-binding site
B)Non-competetive: bound to another part of the E. Allosteric, feedback

18

Controlling enzyme action

1. Regulation of its conc. by repressing/inducing its synthesis
2. Red. by inhibitors/incr. by effectors: allosteric phosphorylation, zymogen, isoenzymes, modulator proteins (CAP)

19

Gene induction

Turning on of transcription = incr. mRNA prod.

20

Gene repression

Turning off of transcription = drcr. mRNA prod.

21

Allosteric regulation

The molec. bind to an allosteric site, sep. from the active site, and inhib./stim. the enzyme activity

22

Feedback inhibition

A type of allosteric regulation. The final product is an allosteric inhib. of the first enzyme in the pathway.

23

Phosphorylation

Covalent modification of an enzyme, by addition of a specific funct. gr. -> activate/inhib. the enzyme

24

Zymogen activation

Covalent modification of an enzyme.
-Zymogen=proenzyme; inactive precursor form of enzyme
-Activation site=site of cleavage
-Activated by specific regulatory protease

25

Isoenzymes

Differ slightly in aa. sequence and consequently in catalytic properties. Have diff. Km.
-Isoform A: high Km-works best in tissues w. high S-conc.
-Isoform B: low Km-works best in tissues w. low S-conc.

26

Oxidoreductases

One oxidiced, one reduced

27

Transferases

Transfer groups.
1.Aldehyde-, ketotransferase
2.Acyltransferase
3.Aminotransferase
4.Phosphotransferase
5.C1 fragments

28

Hydrolases

Hydrolytic cleavage of diff. bonds.
1.Esterases
2.Glycosidases
3.Peptidases
4.Amidases

29

Lyase synthase

Elimination/addition, without breakdown of ATP

30

Isomerases

Isomerization

31

Lyase synthetase

(ATP). Joining of two molecules, without breakdown of atp.