Abstract
The bovine filarial worm Setaria cervi was found to have abundance of gamma-glutamyl transpeptidase (gamma-GT; EC 2.3.2.2) activity. The enzyme activity was almost evenly distributed in subcellular fractions. K-m and V-max of triton X-100 solubilized microsomal gamma-GT towards L-gamma-glutarnyl-p-nitroanilide were calculated to be 0.13 +/- 0.01 mM and 0.03 +/- 0.002 mu mol/min/mg protein, respectively. Similar kinetic parameters for cytosolic fraction were determined to be 0.21 +/- 0.06 mM and 0.45 +/- 0.17 mu mol/min/mg protein, respectively. No remarkable effect by any of the studied amino acids at 1 mM concentration on the enzyme activity was found except L-cystine, which caused concentration dependent increase in enzyme activity while GSH and GSSG caused concentration dependent decrease in enzyme activity. The K-i values for GSH and GSSG were calculated to be around 3.5 +/- 0.50 and 0.85 +/- 0.05 mM, respectively, for microsomal enzyme, whereas 11.0 +/- 1.41 and 0.9 +/- 0.14 mM respectively, for cytosolic gamma-GT. Filarial gamma-GT was also inhibited by L-serine in the presence of borate, K, being calculated to be 1.58 +/- 0.38 mM and 1.13 +/- 0.18 mM for microsomal and cytosolic fractions, respectively. Ki value for standard mammalian inhibitor acivicin was found 0.88 +/- 0.18 mM and 0.28 +/- 0.04 mM for microsomal and cytosolic fractions, respectively.