Enzymes

Question 1

Disorders associated with acid-base inbalances

Answer 1

Acidosis : Blood pH 7.43

Question 2

Enzyme Specificity

Answer 2

Proteases cleave peptide bonds ad specific sites

Question 3

Evidence of enzyme substrate complex?

Answer 3

The limit in reaction rate is due to substrate occupying all available catalytic sites (indirect evidence)
Direct X-ray crystallography evidence
Cytochrome p450 bounds to its substrate camphor
Surrounded by residues of the active site and a heme cofactor

Question 4

Active Site

Answer 4

Takes up small volume. cleft or crevice formed in protein regions.
Specificity depends on the precisely defined arrangement of atoms on the active site.
Unique microenvironment
Void of water, and controls proper shape, pH and polarity for substrate binding and chemical reactivity.

Question 5

Michaelis-Menten eq

Answer 5

V0 = Vmax * ([S] / ([S]+Km)) Km = substrate conc when rate is half its maximal value

Question 6

Oxidoreductases

Answer 6

Transfer electrons from a donor (reducing agent) to an acceptor (oxidizing agent).

Question 7

Transferases

Answer 7

Transfer a functional group (amino, phosphate etc…) between molecules

Question 8

Isomerases

Answer 8

Rearrange molecules

Question 9

Lyases (synthases)

Answer 9

Add or remove atoms (i.e. water, ammonia or CO2) to form a double bond

Question 10

Ligases (synthetases)

Answer 10

Form bonds with the hydrolysis of ATP (C-O, C-S, C-N, C-C)

Question 11

Hydrolases

Answer 11

Cleave bonds via the addition of water

Question 12

Cofactor what it is, and nomenclature

Answer 12

Small molecules that contribute to the rxn of the enzyme
Enzymes that share cofactors share similar mechanisms

Nomenclature

• apoenzyme : No-cofactor
• Haloenzyme: Bound to cofactor and catalytically active

Question 13

Types of Cofactors

Answer 13

Metals (positively charged)
Stable coordination of active site groups
Ex. Zinc activates H20 to form OH- nucleophile
Small organic molecules derived from vitamins

Question 14

Diseases associated with cofactor deficiencies

Answer 14

Scurvy : Vitamin C is a cofactor for lysyl hydroxylase - involved in collagen assembly
Spongy gums, hemorrhaging of skin

Ariboflavinosis : riboflavin in B2 required for FAD synthesis
Causes reduced glutathione reductase activity - requires FAD
Lesions in corner of mouth and on lips, UV sensitive

Question 15

Michaelis-Menten again

Answer 15

V0 = Vmax + [S] / ([S]+Km) Km = vmax/2

Question 16

Lineweaver-Burk Plot

Answer 16

Taking the double reciprocal of the michaelis-menten (makes it possible to solve for Km and Vmax)

Question 17

Sir Archibald Edward Garrod

Answer 17

Made connection between disease and fundamental errors in biochemical rxns (recognized relation between disease and mendelian genetics, alkaptonuria)
Coined term “inborn errors of metabolism”
Enzymes must be link

Question 18

Three types of inhibitors

Answer 18

Competitive (at binding site) increase Km
Noncompetitive (Binds away from binding site that prevents enzyme binding) Affects only the Vmax
Uncompetitive (Binds away from binding site but doesn’t prevent enzyme binding) Binds only to the enzyme-substrate complex. Both Km and Vmax are altered

Question 19

Reversible vs. irreversible

Answer 19

Reverse: bind to enyzmes with noncovalent interactions such as H+ bonds, can easily be removed by dilution or dialysis
ex: HIV protease inhibitors mimics the enymes’ substrates

Irreversible Inhibition: covalently modifies an enzyme, therefore cannot be reversed. Alter the active site

Question 20

Competitive inhibitor and lineweaver-burk plot

Answer 20

Changes the slop, thus creating a new X-intercept (-1/Km)

Question 21

Uncompetitive and lineweaver-burk plot

Answer 21

Changes the y-intercept (1/Vmax), creating a new Vmax and Km (-1/Km)
They are both reduced

Question 22

Noncompetitive and lineweaver-burk plot

Answer 22

Same X-intercept (-1/Km), but different slope thus creating a new Vmax which will be decreased