Kinetic distinction between rapid-equilibrium random and abortive ordered enzymatic mechanisms using alternative substrates or kinetic isotope effects.
Alternative substrates, such as those isotopically-labeled, which differ in their rate constants of catalysis but not in their rate constants of binding, generate identical values of V/Ka in ordered kinetic mechanisms of bireactant enzymes. This is shown to be true even for the rapid-equilibrium ordered mechanism in which an abortive complex between free enzyme and the second substrate is formed. In contrast, rapid-equilibrium random mechanisms have non-identical values for V/Ka. Consequently, the effect of alternative substrates or isotope effects on V/Ka provides a means to distinguish between these nearly identical kinetic mechanisms.
Gates
C A
CA
Division of Pharmaceutical Biochemistry, School of Pharmacy, University of Wisconsin, Madison 53706.
Northrop
D B
DB
D004798:Enzymes / Q000378:metabolism*; D007553:Isotope Labeling / Q000379:methods; D007700:Kinetics; D008433:Mathematics; D008962:Models, Theoretical; D009713:Nucleotidyltransferases / Q000378:metabolism
D004798:Enzymes; D009713:Nucleotidyltransferases; C020565:gentamicin 2''-nucleotidyltransferase