Enzyme

The induced-fit hypothesis: The substrate molecule binds with the enzyme molecule and induces a change in shape of the enzyme molecule.

Enzyme Cofactors
A cofactor is the non-protein component of an enzyme essential for its catalytic activity.

Inorganic ions= Activators
can be loosely or firmly bound

Organic compounds:

1. firmly bound = prosthetic group
2. loosely bound = coenzymes

----Prosthetic group
----integral part, e.g. FAD

----Coenzymes
----carrier to transfer atom, e.g. NAD, NADP

Enzyme Inhibitions (nothing to do with cofactor)

Competitive inhibitors:
substance similar to substrate, compete for active site
+ substrate concentration, - degree of inhibition, vice versa
+ inhibitor concentration, + degree of inhibition, vice versa

Non-competitive inhibitors:
attach to parts other than active site, not compete for active site
+ substrate concentration, X degree of inhibition, vice versa
+ inhibitor concentration, + degree of inhibition, vice versa
binding affinity

Reversible inhibitors
Can be Competitive or Non-competitive
Effect on enzyme:
occupying active site/altering conformation of active site temporarily

Irreversible inhibitors
ONLY NON-COMPETITIVE
Effect on enzyme:
altering conformation of active site permanently

End-product inhibition

Metabolic pathway:
Step-wise reaction for

1. preventing vigorous reaction that a quick release of heat may damage the cells
2. allowing the energy released from the reactions to be utilized effectively
3. intermediate metabolites of pathway may be useful to other metabolic pathways

Negative feedback inhibition:
When end-product is in excess, end product itself act as an allosteric inhibitor and binds with the allosteric site of allosteric enzyme. This will temporary shut down the entire series of reaction.
All the intermediate metabolites and the end-product will not be formed.