Gamma glutamyltransferase ammonia production from glutamine: effect of physiological glutathione concentration |
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| Authors: | P D Dass T C Welbourne |
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| Institution: | 1. School of Life Sciences, Zhengzhou University, Zhengzhou 450001, Henan, China;2. Henan Provincial People''s Hospital, Zhengzhou 450003, Henan, China;3. Clinical Laboratory, Zhumadian Hospital of Traditional Chinese Medicine, Zhumadian 463000, Henan, China;4. Department of Surgery, Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH 43210, USA |
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| 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. |
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