Ahmad S, Bhatnagar R K, Venkitasubramanian T A
Department of Biochemistry, V.P. Chest Institute, University of Delhi, India.
Ann Inst Pasteur Microbiol. 1986 Nov-Dec;137B(3):231-7. doi: 10.1016/s0769-2609(86)80114-4.
Glutamate dehydrogenase (aminating) and glutamine synthetase activities were assayed in Mycobacterium smegmatis following growth on various carbon and nitrogen sources. The activities (expressed as nmoles product formed/min/mg crude extract protein) of these two enzymes were higher in crude extracts from glucose-grown cells than in glycerol- or fructose-grown cells. In the presence of succinate, pyruvate, fumarate or acetate in the growth medium, both these enzyme activities were lower than those in citrate-grown cells. The glutamate dehydrogenase (GDH) activity was the same in asparagine and glutamine-grown cells. Ammonium chloride, alanine or glutamic acid, when used as nitrogen source, resulted in low GDH activity as compared to asparagine-grown cells. Glutamine synthetase activity was considerably lower (2-4 fold) when the cells were grown on alanine, glutamine, glutamic acid or ammonium chloride as the nitrogen source than those in asparagine-grown cells. Glutamate and ammonium chloride, when present in the growth medium, repressed both glutamate dehydrogenase and glutamine synthetase, though the degree of repression was small. The results suggest that only a weak transcriptional control operates for these enzyme activities in M. smegmatis.
在耻垢分枝杆菌于各种碳源和氮源上生长后，测定了谷氨酸脱氢酶（氨基化）和谷氨酰胺合成酶的活性。这两种酶的活性（以每分钟每毫克粗提物蛋白形成的产物纳摩尔数表示）在葡萄糖培养的细胞粗提物中高于甘油或果糖培养的细胞。在生长培养基中存在琥珀酸盐、丙酮酸、富马酸盐或乙酸盐时，这两种酶的活性均低于柠檬酸盐培养的细胞。在天冬酰胺和谷氨酰胺培养的细胞中，谷氨酸脱氢酶（GDH）活性相同。与天冬酰胺培养的细胞相比，当氯化铵、丙氨酸或谷氨酸用作氮源时，GDH活性较低。当细胞以丙氨酸、谷氨酰胺、谷氨酸或氯化铵作为氮源生长时，谷氨酰胺合成酶活性比天冬酰胺培养的细胞低得多（2至4倍）。当生长培养基中存在谷氨酸和氯化铵时，会抑制谷氨酸脱氢酶和谷氨酰胺合成酶，尽管抑制程度较小。结果表明，在耻垢分枝杆菌中，对这些酶活性仅存在较弱的转录控制。
