Kinetics and thermodynamics of transpeptidation catalysed by Bacillus subtilis gamma glutamyl transferase
| Title | Kinetics and thermodynamics of transpeptidation catalysed by Bacillus subtilis gamma glutamyl transferase |
| Publication Type | Journal Article |
| Year of Publication | 2017 |
| Authors | Balakrishna, S, Prabhune, AA |
| Journal | Indian Journal of Biochemistry and Biophysics |
| Volume | 54 |
| Issue | 3-4 |
| Pagination | 109-113 |
| Date Published | JUN |
| Type of Article | Article |
| Abstract | Gamma 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 unaltered |
| Type of Journal (Indian or Foreign) | Indian |
| Impact Factor (IF) | 0.385 |
Divison category:
Biochemical Sciences