Kumar S, Ojha V, Ganguly N K, Kohli K K
Department of Biochemistry, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Biochem Int. 1990;20(3):539-48.
The presence of gamma glutamyl transferase (GGT) has been established in Mycobacterium smegmatis. The 10,000 x g supernatant demonstrated only hydrolase activity and did not exhibit any transpeptidase activity. Most of the transferase activity was recovered in 100,000 x g supernatant demonstrating that GGT is a cytosolic enzyme. Maximum activity of GGT was observed at two days of growth and the activity decreased significantly till the seventh day of growth when mycobacteria was grown as stationary culture. The km for gamma glutamyl-p-nitroanilide was found to be 0.074 mM and Vmax for the reaction approached 11.9 nmol per min per mg protein. L-serine + borate was found to be a competitive inhibitor (Ki 12.05 mM) for GGT activity. The pH optimum for GGT activity was observed between 7.5 to 8.5 and temperature above 35 degrees C rapidly inactivated the enzyme activity. To the best of our knowledge, this is the first report which unequivocally establishes the presence of GGT activity in 10,000 x g supernatant of M. smegmatis.
耻垢分枝杆菌中已证实存在γ-谷氨酰转移酶（GGT）。10000×g离心上清液仅显示水解酶活性，未表现出任何转肽酶活性。大部分转移酶活性在100000×g离心上清液中得以恢复，这表明GGT是一种胞质酶。当分枝杆菌以静置培养方式生长时，在生长两天时观察到GGT的最大活性，且直到生长第七天该活性显著下降。γ-谷氨酰对硝基苯胺的米氏常数（km）为0.074 mM，该反应的最大反应速度（Vmax）接近每分钟每毫克蛋白质11.9 nmol。发现L-丝氨酸+硼酸盐是GGT活性的竞争性抑制剂（抑制常数Ki为12.05 mM）。观察到GGT活性的最适pH在7.5至8.5之间，温度高于35℃会使酶活性迅速失活。据我们所知，这是第一份明确证实耻垢分枝杆菌10000×g离心上清液中存在GGT活性的报告。
