Six classes of enzymes. Factors affecting enzyme activity. Post-transcriptional modification/ Regulatory events pH Temperature Enzyme or Substrate concentration Cofactors. What do enzymes do?. A catalyst is a substance that accelerates a chemical reaction without itself
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A catalyst is a substance
that accelerates a chemical
reaction without itself
undergoing any net change
Transition state vs. Ground State theory
Do enzymes accelerate catalysis by putting substrates
in close proximity?
As Pauling, among others, suggested is catalysis a
result of an enzyme having a higher affinity for the
Still to this day a topic of debate, but presently it seems to be
a little of both
E + S E + (S)*
E + S ES (ES)*
= [E][S]*/[ES]* = [(kcat/Km)/knon]-1
Affinity for the Transition state
For Triosephosphate isomerase KTS = 10-12, and Km = 10-4
Thus, this enzyme binds the transition state eight orders of magnitude
more strongly than the substrate.
developments in analogs and catalytic antibodies
General acid-base catalysis
Metal Ion catalysis (nucleophile,
Hexokinase catalytic mechanism illustrates an additional important principle