γ-谷氨酰转移酶由谷氨酰胺生成氨：生理浓度谷胱甘肽的影响。

Gamma glutamyltransferase ammonia production from glutamine: effect of physiological glutathione concentration.

作者信息

Dass P D, Welbourne T C

出版信息

Life Sci. 1986 Apr 7;38(14):1305-8. doi: 10.1016/0024-3205(86)90424-8.

Abstract

The formation of ammonia from physiological glutamine concentration catalyzed by gamma glutamyltransferase was studied in the presence of physiological glutathione concentration. The apparent Km for ammonia formation from glutamine was 1.6 mM some 2 fold greater than the actual plasma concentration. In the presence of 30 microM glutathione neither the apparent Km or Vmax were changed. At supraphysiological glutathione concentration, 1mM, the apparent Km was increased while the Vmax decreased to one third. Hippurate the physiological modulator of the enzyme's glutaminase activity reduced the Km to 0.9 mM, the physiological range, and elevated the Vmax 2.7 fold.

摘要

在生理谷胱甘肽浓度存在的情况下，研究了γ-谷氨酰转移酶催化从生理谷氨酰胺浓度形成氨的过程。从谷氨酰胺形成氨的表观Km为1.6 mM，约为实际血浆浓度的2倍。在存在30 microM谷胱甘肽的情况下，表观Km和Vmax均未改变。在超生理谷胱甘肽浓度（1 mM）下，表观Km增加，而Vmax降至三分之一。该酶谷氨酰胺酶活性的生理调节剂马尿酸盐将Km降低至0.9 mM（生理范围），并使Vmax提高2.7倍。