(CH 6) Additional factors for maximal enzyme activity

Prosthetic Group

*some need

• small organic molecule permanently bound to enzyme

Coenzyme

sm organic molecule that temporarily binds to an enzyme

(cofactors or metal ions)

Coenzyme function

• May be required for proper 3D shape of protein

• May be directly involved in chemical reaction

Coenzymes make temp bonds between

2 substrates

T/F Coenzymes do not change the shape of the active site

F

They can change the shape of the active site 

Inhibitor

molecule or ion that binds to enzyme and decreases its activity

Competitive Inhibitors

• binds to active site of enzyme

• inhibitors must resemble the substrate in order to bind to the active site

What happens if the inhibitor binds to the active site?

• the substrate can’t bind

• NO reaction

Competitive Inhibitors

The (blank) inhibitor binds to the active site to (blank) the reaction rate 

more, lower

Competitive Inhibitors have similar structure to (blank)

the normal structure

• binds to the active site

Noncompetitive Inhibitors

• binds to the enzyme noncovalently at the allosteric site

Catalytic subunit

binds substrate at the active site and will preform the reaction

Regulatory subunit 

binds an effector at the allosteric site and will regulate enzyme activity

Effector

Small organic molecule that controls the activity of the enzyme

Effector binds to (blank)

the allosteric site

Active form vs Inactive form

• form of the enzyme that performs its function (ON)

• nonfunctional form of enzyme (OFF)

Feedback Inhibition

when a product made at the end of the pathway binds to one of the enzymes near the beginning of the pathway and inactivates the enzyme.

Allosteric Regulation

type of noncompetitve inhibition

• regulates enzymes in pathways

• feedback inhibition is a type of this

Allosteric Inhibitor

binding of the effector, makes enzyme less active

Allosteric Activator

binding the effector makes the enzyme more active