• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
Enzyme regulation
 

Enzyme regulation

on

  • 366 views

 

Statistics

Views

Total Views
366
Views on SlideShare
366
Embed Views
0

Actions

Likes
0
Downloads
0
Comments
0

0 Embeds 0

No embeds

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

    Enzyme regulation Enzyme regulation Presentation Transcript

    • Enzyme Regulation
    • REGULATION OF ENZYME ACTIVITY Enzyme quantity – regulation of gene expression (Response time = minutes to hours) a) Transcription b) Translation c) Enzyme turnover
    • Enzyme activity (rapid response time = fraction of seconds) Allosteric regulation Covalent modification Association-disassociation’ Proteolytic cleavage of proenzyme
    • ALLOSTERIC REGULATION End products are often inhibitors Allosteric modulators bind to site other than the active site Allosteric enzymes usually have 4 o structure Vo vs [S] plots give sigmoidal curve for at least one substrate Can remove allosteric site without effecting enzymatic action
    • REGULATION OF ENZYME ACTIVITY (BIOCHEMICAL REGULATION) 1 st committed step of a biosynthetic pathway or enzymes at pathway branch points often regulated by feedback inhibition. 1 A 2 C B X H 4” I 3” 3’X E 4’ F 5” 5’ J G Efficient use of biosynthetic precursors and energy
    • PHOSPHOFRUCTOKINASE( PFK) Fructose-6-P+ATP ---> Fructose-1,6-bisphosphate + ADP •PFK catalyzes 1st committed step in glycolysis (10 steps total) (Glucose + 2ADP + 2 NAD+ + 2Pi  2pyruvate + 2ATP + 2NADH) •Phosphoenolpyruvate is an allosteric inhibitor of PFK •ADP is an allosteric activator of PFK
    • ALLOSTERIC MODULATORS BIND TO SITE OTHER THAN THE ACTIVE SITE AND ALLOSTERIC ENZYMES HAVE 4 O STRUCTURE Fructose-6-P + ATP -----> Fructose-1,6-bisphosphate + ADP ADP Allosteric Activator (ADP) binds distal to active site
    • VO VS [S] PLOTS GIVE SIGMOIDAL CURVE FOR AT LEAST ONE SUBSTRATE Binding of this allosteric inhibitor or this activator does not effect Vmax, but does alter Km Allosteric enzyme do not follow M-M kinetics
    • ALLOSTERIC T TO R TRANSITION I ET-I I S ET Concerted model ER Sequential model S ER-S
    • COVALENT MODIFICATION •Regulation by covalent modification is slower than allosteric regulation •Reversible •Require one enzyme for activation and one enzyme for inactivation •Covalent modification freezes enzyme T or R conformation
    • PHOSPHORYLATION /DEPHOSPHORYLATION •Most common covalent modification • Involve protein kinases/phosphatase •PDK inactivated by phosphorylation •Amino acids with –OH groups are targets for phosphorylation •Phosphates are bulky (-) charged groups which effect conformation
    • ENZYME REGULATION BY ASSOCIATION/DISASSOCIAT ION Carboxylase •Acetyl-CoA •acetyl-CoA + CO2 + ATP  malonyl-CoA + ADP + Pi •1St committed step in fatty acid biosynthesis •In presence of citrate activated •In presence of fatty acyl-CoA inactivated citrate polymerized unpolymerized Fatty acyl-CoA
    • PROTEOLYTIC CLEAVAGE OF PROENZYME(ZYMOGEN)
    • PROINSULIN TO INSULIN
    • BLOOD CLOTTING •Clotting involves series of zymogen activations •Seven clotting factors are serine proteases involved in clotting cascade rxns
    • X X X X X X