01418nas a2200145   4500008004100000245008900041210006900130260000800199300001200207490000600219520088100225100002501106700002101131856012001152       2013                        eng d00aGamma-glutamyl transferases: a structural, mechanistic and physiological perspective0 aGammaglutamyl transferases a structural mechanistic and physiolo  cJAN  a51–650 v93 a<p>Gamma glutamyl transferases (GGT) are highly conserved enzymes that occur from bacteria to humans. They remove terminal γ-glutamyl residue from peptides and amides. GGTs play an important role in the homeostasis of glutathione (a major cellular antioxidant) and in the detoxification of xenobiotics in mammals. They are implicated in diseases like diabetes, inflammation, neurodegenerative diseases and cardiovascular diseases. The physiological role of GGTs in bacteria is still unclear. Nothing is known about the basis for the strong conservation of the enzyme across the living system. The review focuses on the enzyme’s physiology, chemistry and structural properties of the enzyme with emphasis on the evolutionary relationships. The available data indicate that the members of the GGT family share common structural features but are functionally heterogenous.</p>1 aBalakrishna, Sharath1 aPrabhune, Asmita  uhttps://library.ncl.res.in/content/gamma-glutamyl-transferases-structural-mechanistic-and-physiological-perspective01797nas a2200145   4500008004100000022001400041245009700055210006900152260000800221300001100229520125100240100002501491700002101516856011401537       2014                        eng d  a1537-744X00aEffect of pH on the hydrolytic kinetics of gamma-glutamyl transferase from bacillus subtilis0 aEffect of pH on the hydrolytic kinetics of gammaglutamyl transfe  cFEB  a2162703 a<p>The effect of pH on the steady state kinetics of gamma-glutamyl transferase (GGT) from Bacillus subtilis was examined using glutamyl-(3-carboxyl)-4-nitroanilide as the chromogenic reporter substrate. The enzyme was active in the pH range 7.0-11.0 with the optimum activity at pH 11.0. We noticed a pH dependent transformation in the nature of substrate consumption kinetics. The substrate saturation curves were hyperbolic in the pH range 7.0-9.0 but changed into sigmoid form at pH 10.0 and 11.0. Hill's coefficients were &gt; 1. We also analysed the effect of pH on the structure of the enzyme. The circular dichroism spectra of the enzyme sample at pH 9.0 and 11.0 were coincidental in both far and near UV regions indicating conservation of the secondary and tertiary structures, respectively. Themolecular weight of the enzyme sample was the same in both pH 7.0 and 11.0 indicating conservation of the quaternary structure. These results show that the kinetic transformation does not involve significant conformational changes. Cooperative binding of multiple substrate molecules may not be the basis for the sigmoid kinetics as only one substrate binding site has been noticed in the reported crystal structures of B. subtilis GGT.</p>
1 aBalakrishna, Sharath1 aPrabhune, Asmita  uhttps://library.ncl.res.in/content/effect-ph-hydrolytic-kinetics-gamma-glutamyl-transferase-bacillus-subtilis01869nas 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