Factors Affecting Enzyme Kinetics

A. Enzyme concentration

Probably the most important method in biology

Control via gene expression: transcription and translation

B. Substrate concentration

May be important in preventing reactions...
compartment enzyme away from substrate

C. Cofactor presence

1. Metal ions esp. in electronic rxns
2. Coenzymes (ATP, NADPH, etc.) esp. in redox reactions:
   
   

D. Allosteric regulators

1. Inhibitors--Catalytic Site on Enzyme
2. Promoters--Allosteric Site on Enzyme

   Example: Phosphofructokinase (Glycolysis)
       Inhibited by citrate from Kreb's cycle
       Promoted by high ADP & AMP concentration

E. Inhibitors

1. Competitive

   E + S <-> ES <-> E + P

   E + I <-> EI (no product)

   1. I combines at active site of enzyme
   2. I must resemble S
   3. Combination reversible
   4. Inhibition reduced by adding more substrate

      

2. Non-competitive

   Heavy Metals: Hg As Pb attack SH Groups

   Minimata Bay Incident in Japan

F. Temperature

G. pH

Amino Acids with Acidic R-Group: glu asp
Amino Acids with Alkaline R-Group: arg lys his

Charges change on R-group with pH
This alters conformation of protein = enzyme activity

H+ supresses COOH ionization to COO^- + H⁺
H⁺ increases NH₂ protonation to NH₃⁺

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