lecture 11 definitions

Regulation, vitamins, and diagnostic enzymes

Competitive inhibitor

Inhibitor is a molecule that resembles the substrate and competes for the same binding site on the enzyme.

Noncompetitive inhibitor

Structure of inhibitor does not resemble the substrate and binds to a seperate site on the enzyme causing a change in active site configuration thus preventing the substrate from binding.

Uncompetitive inhibitor

Structure of the inhibitor does not resemble the substrate and binds to the enzyme-substrate complex but not at the active site. It can’t bind the enzyme alone;.

Irreverisble inhibition

Covalent modification of enzyme rendering it inactive.

Allosteric regulation (+ or -)

Substrate binding at the active site is effected by the binding of a molecule at a different site. (positive regulator/effector increases activity of enzyme/turns it on; negative regulator decreases/shuts off enzyme.

Feedback control (+ or -)

A product in a metabolic pathway is an allosteric regulator of an enzyme that catalyzes a critical step in that pathway.

Covalent modification

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

Zymogens

Enzyme is synthesized as an inactive form (proenzyme), which has a longer protein segment that must be removed before enzyme is active.

Genetic control

Gene for enzyme is turned off or on to regulate the amount of enzyme present in cell.

Km = ?

The enzyme’s affinity for the substrate.

Inhibition is competitive when?

The inhibitor resembles the substrate.

Negative allosteric regulation uses which type of inhibition?

Noncompetitive

The lower the Km value…

The higher the enzyme’s affinity is for the substrate.

The substrate cannot enter the active site in:

Negative allosteric regulation

The substrate can enter in:

Positive allosteric regulation

In negative feedback control:

The product inhibits the first enzyme to save energy.

In positive feedback control:

The product enhances activity of the first enzyme.

Which type of inhibition is the results of a covalent modification of an amino acid in the active site of the enzyme?

Irreversible inhibition

Which vitamins are hydrophilic?

Water soluble vitamins

Which vitamins contain OH and COOH groups?

Water soluble vitamins

Which vitamins form coenzymes?

Water soluble vitamins

Which vitamins are hydrophobic?

Fat soluble vitamins

Which vitamins are stored in the liver?

Fat soluble vitamins

Which vitamins are predominantly made of Carbon and Hydrogen atoms?

Fat soluble vitamins

Which vitamins are NOT water soluble?

K, A, D, E

Vitamin K active form:

Phylloquinone

Vitamin A active form:

Retinol

Vitamin E active form:

tocopherol

Vitamin D active form:

calciferol

Vitamin C

Ascorbic Acid

Vitamin B1

Thiamine

Vitamin B2

Riboflavin

Vitamin B3

Niacin

Vitamin B5

Pantothenic Acid

Vitamin B6

Pyridoxine

Vitamin B7

Biotin

Vitamin B9

Folic Acid

Vitamin B12

Cobalmine

Provitamin of Vitamin A

B-carotene

Function of Vitamin A

Vision; cell growth & differentiation, antioxidant for lipids

Provitamin of Vitamin D

7-Dehydrocholesterol

Function of Vitamin D

Required for normal bone growth, increases absorption of Ca2+ and phosphate in gut and retention in kidneys.

Function of Vitamin E

Strong antioxidant – stops production of reactive oxygen

species (ROS)

- Prevents oxidative damage of LDLs & cell membranes

- Prevent the formation of blood clots

What is tocopherol regenerated by?

The oxidation of Vitamin C

Function of Vitamin K

Required for the formation of prothrombin, which converts into thrombin (a vital enzyme involved in the formation of blood clots), bone metabolism.

True or False: Coenzymes are made out of soluble vitamins and can diffuse in and out of enzymes.

True

Vitamin B1 (Thiamine) Coenzyme:

Thiamine pyrophosphate (TPP)

Vitamin B1 Function:

required for carbohydrate metabolism

-decarboxylation of substrates & synthesis of ribose

Vitamin B2 Coenzyme:

FMN (flavin mononucleotide)

FAD/FADH2 (flavin adenine dinucleotide)

Vitamin B2 function:

Redox reactions

Vitamin B3 coenzyme:

nicotinamide adenine dinucleotide

NAD+/NADH, NADP+/NADPH

Vitamin B3 function:

Redox reactions

NAD+ is the _______ form of the coenzyme derived from Niacin.

Oxidized.

Vitamin B5 coenzyme:

Coenzyme A

Vitamin B5 function:

Carrier of acetyl groups (2 carbon groups into TCA cycle)

Vitamin B6 coenzyme:

phosphate form (PLP), Coenzyme for Transaminase -transfers amine between amino acids & Keto acids

Vitamin B6 function:

Amino acid metabolism

Vitamin B7 coenzyme:

Biotin or Biocytin

Vitamin B7 function:

Carbon carrier in Carbohydrate and Lipid metabolism, Forms amide bonds with amine groups on proteins

Vitamin B9 coenzyme:

Tetrahydrofolate

Vitamin B9 function:

carrier of 1 carbon units in the formation of heme, nucleic acids & choline; protects against cardiovascular disease

Possible birth defects from lack of Folic acid:

spina bifida, neutral tube disorders

Why is Folic acid chemotherapuetic?

Methotrexate interferes with conversion to THF; therefore, no synthesis of deoxyribonucleic acids; no DNA replication

Vitamin B12 coenzyme:

Methylcobalamin (2 forms)

Vitamin B12 function:

Methyl transfer, Nucleic acid metabolism

Condition associated with Vitamin B12/Cobalamin

Pernicious anemia: (large, fragile, immature RBC), produces gastrointestinal disorders, spinal cord lesions w/ lack of muscle coordination

Vitamin C coenzyme:

self (essential)

Vitamin C function:

Antioxidant (reduces iron & vitamin E); Energy production; Disease prevention; Collagen formation

An antioxidant is a/an ________ because it gets oxidized while a substrate gets reduced.

Reducing agent

True or False: Testing for a specific enzyme activity in your blood can aid in identifying organ damage.

True

Lateral flow uses what class of protein to identify antigens in a sample?

Protective