Enzyme regulation and Vitamin Memorization

Competitive inhibition

Inhibitor resembles the substrate and competes for the same binding site on the enzyme

Replacing the snack with a different one

Uncompetitive inhibition

Binds to part of the enzyme-substrate complex to trap the substrate or prevent it from binding

Noncompetitive inhibition

Binds to a separate site on the enzyme, causing it to change the configuration of the active site.

Irreversible inhibition

Destruction of the enzyme and substrate by covalent modification

Km = Vmax/2

Substrate-enzyme affinity equation

Lower

The ______ the Km, the greater the enzyme’s affinity for the substrate

unchanged, increased

In a competitive inhibitor, Vmax is _____ but Km is ______

Lowered, unchanged

In a non-competitive inhibitor, Vmax is _____, Km is _________

Lowered, lowered

In an uncompetitive inhibitor, Vmax is _____ and Km is ______ by the same ratio

Allosteric Regulation (positive and negative)

Substrate binding at the active site is affected by the bonding of a molecule at a different site. Negative = Non-competitive inhibition

Feedback control

A product in the metabolic pathway becomes an allosteric regulator of an enzyme that either catalyzes or inhibits the reaction.

Covalent modification

Addition of a phosphate group on tyrosine, serine, or theronine residue triggers conformational change in enzyme structure that activates or deactivates.

Zymogens

Enzyme is synthesized in proenzyme for, and then a longer enzyme strain must be removed for the enzyme to activate. 

Genetic control

Gene of an enzyme is turned off or on to regulate the amount of enzyme present.

Hydrophillic

Contain OH and COOH groups

Not stored in body

Form coenzymes

Water-soluble vitamins

Hydrophobic

Carbon and Hydrogen atoms

Stored in liver

Fat-soluble vitamins

C,B1-B7, B9, B12

What are the water-soluble vitamins

A, D, E, K

What are the fat-soluble vitamins

B-carotene

Retinol

Vision; cell growth & differentiation; antioxidant for lipids

Vegetables

Vitamin A

7-dehydrocholesterol

Calciferol

Required for bone growth as it absorbs calcium and phosphate

Sun, fatty fish

Vitamin D

No provitamin form

Alpha tocopherol

Strong antioxidant - stops production of damaging oxygen species

Wheat, grain, nuts

Vitamin E

No provitamin form

Phylloquinone

Required for the formation of prothrombin - essential in forming blood clots; bone metabolism

Spinach, leafy vegetables

Vitamin K

Coenzymes

Water-soluble vitamins travel through the bloodstream and are modified by enzymes to become…

Thiamine

Thiamine Pyrophosphate (TPP)

Required for carbohydrate metabolism and synthesis of ribose

Bread, milk

Vitamin B1

Riboflavin

FMN, FADH/FADH2

Redox reactions

Bread, milk

Vitamin B2

Niacin

NAD+/NADH; NADP+/NADPH

Redox reactions

Vitamin B3

Oxidized - less bonds to hydrogen than NADH

NAD+ is an _______ molecule

Pantothenic acid

Coenzyme A (CoA)

Carrier of acetyl groups

Nearly all food

Vitamin B5

Pyroxidine

PLP

Amino acid metabolism

Green leafy veggies

Vitamin B6

Biotin

Biocytin

Carbon carrier in carbohyrates; forms amide bonds with amine groups on proteins

Eggs, meat, veggies

Vitamin B7

Folic acid

Tetrahydrofolate (THF)

Carrier of 1 carbon units to form heme, nucleic acids; prevents cardiovascular disease; REQUIRED for DNA replication

Green leafy vegetables

Vitamin B9

Cobalamin

Methylcobalamin

Methyl transfer, nucleic acid metabolism

Vitamin B12

L-ascorbic acid

None

Antioxidant that reduces vitamin E; forms collagen in bones

Citrus fruits, cabbage

Vitamin C