(V/K) kinetic isotope effect and steady-state kinetic analysis for the transglutaminase 2 catalyzed deamidation and transamidation reactions.
Evan A Wells, Mark A Anderson, Tonya N Zeczycki
Author Information
Evan A Wells: Department of Biochemistry and Molecular Biology and the East Carolina Diabetes and Obesity Institute, Brody School of Medicine at East Carolina University, Greenville, NC, United States.
Mark A Anderson: Department of Biochemistry, University of Wisconsin, Madison, WI, United States.
Tonya N Zeczycki: Department of Biochemistry and Molecular Biology and the East Carolina Diabetes and Obesity Institute, Brody School of Medicine at East Carolina University, Greenville, NC, United States. Electronic address: zeczyckit@ecu.edu.
The Ca-dependent deamidation and transamidation activities of transglutaminase 2 (TG2) are important to numerous physiological and pathological processes. Herein, we have examined the steady-state kinetics and (V/K) kinetic isotope effects (KIEs) for the TG2-catalyzed deamidation and transamidation of N-Benzyloxycarbonyl-l-Glutaminylglycine (Z-Gln-Gly) using putrescine as the acyl acceptor substrate. Kinetic parameters determined from initial velocity plots are consistent with previously proposed mechanisms. Significant differences in the (V/K) KIEs on NH release determined for the deamidation (0.2%) and the transamidation (2.3%) of Z-Gln-Gly suggest the rate-limiting steps of TG2 active site acylation are dependent on the presence of the acyl acceptor. We propose a plausible mechanistic explanation where substrate-induced conformational changes may play a role in promoting catalysis.
