Enzymes

What is an apo-enzyme?

A protein molecule which has its own primary, secondary, tertiary and quaternary structure

What is an enzyme?

Enzymes are specific proteins that catalyse biochemical reactions.

Biological catalysts

What is a coenzyme?

Prosthetic group of enzyme which can covalently and non-covalently associate with an apo-enzyme

What is a whole enzyme?

Consists of an apo-enzyme and co-enzyme

What is an enzyme’s active site?

Part of the enzyme which recognises the substrate and performs a catalytic reaction

What is the recognition site?

Part of the active site that recognises the substrate

What is the catalytic site?

Part of the active site that peforms catalysis

How do you name enzymes?

Add -ase to the substrate that the enzyme converts

How many classes are enzymes split into?

6

Name all the classes that enzymes are split into

• Oxidoreductases

• Transferases

• Hydrolases

• Liases

• Isomerases

• Ligases

Oxidoreductases

Catalyses oxidation and reduction reactions

Transferases

Transfers groups of atoms from one molecule to another

Hydrolases

Catalyses reactions involved in hydrolysis

Liases

Attaches functional groups to pi-bonds

Isomerases

Catalyses reactions of isomerisation

Ligases

Catalyses biosynthesis reactions

What does an enzyme’s EC number mean?

Four digits which mean:

1. Class of the enzyme

2. Subclass

3. Sub-subclass

4. Exact enzyme

Describe the enzymatic reaction

What is the allosteric site of an enzyme?

The amino acid sequence recognising and binding to the allosteric modulator (or allosteric inhibitor)

What is allosteric activation?

The allosteric modulator interacts with the allosteric site of the enzyme causing conformational change and activation

What is allosteric inhibition?

The allosteric inhibitor reacts with the allosteric site of the enzyme causing conformational change and inhibition

What is isosteric inhibition?

Inhibitor competes with the substrate for interaction with the active site of the enzyme.

This is normally reversible

What is absolute substrate specificity?

The case when the enzyme could convert only one substrate

What is temperature optimum?

The temperatures at which the enzyme displays maximal activity

What is pH optimum?

The pH value at which the enzyme displays maximal activity

What are iso-enzymes?

Enzymes of different sturctures (but normally similar) which perform the same reactions

What are multi-enzyme systems?

Systems containing several enzymes which catalyse consequent conversions of the same substrate

What does the equation of Michelins-Menthen describe?

The speed of enzyme reaction

What is the Michelin-Menthen equation?