01869nas a2200145   4500008004100000245011000041210006900151260000800220300001200228490000800240520129800248100002501546700002501571856012701596       2017                        eng d00aKinetics and thermodynamics of transpeptidation catalysed by Bacillus subtilis gamma glutamyl transferase0 aKinetics and thermodynamics of transpeptidation catalysed by Bac  cJUN  a109-1130 v54 3 aGamma glutamyl transferases (GGT) catalyse the removal (deglutamylation) of the terminal gamma-glutamate residue from compounds such as glutathione and poly-gamma-glutamic acid and its transfer either to a water molecule (hydrolysis) or to a peptide/amino acid (transpeptidation). We analysed the kinetics of Bacillus subtilis GGT (BsGGT) catalysed transpeptidation using gamma-glutamyl-(3-carboxyl)-4-nitroaniline as the gamma-glutamate-donor and glycylglycine (Gly-Gly) as the gamma-glutamate acceptor. Addition of Gly-Gly improved the affinity (Km) of the enzyme for gamma-glutamyl-(3-carboxyl)-4-nitroaniline by nearly 25 times with negligible impact on the rate of deglutamylation (V-max). The asymmetric changes in the kinetic parameters improved the specificity constant (K-cat/K-m.) by about 43 times. BsGGT catalysed transpeptidation was pronounced in conditions that are unfavorable for hydrolysis. Maximum transpeptidation occurred near neutral pH and when the concentration of the gamma-glutamate-donor substrate is lower. The effect of Gly-Gly on the kinetics of BsGGT is contrastingly different from that observed for eukaryotic GGTs. In the case of mammalian GGTs, the addition of Gly-Gly increases both Km and k(cat); and, the specificity constant (K-cat/K-m) remains unaltered1 aBalakrishna, Sharath1 aPrabhune, Asmita, A.  uhttps://library.ncl.res.in/content/kinetics-and-thermodynamics-transpeptidation-catalysed-bacillus-subtilis-gamma-glutamyl