期刊
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
卷 504, 期 2, 页码 197-203出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.abb.2010.09.002
关键词
Glutaminase; Intestine; Mitochondria; ADP; ATP; Phosphate
资金
- University of KwaZulu-Natal
The effect of adenine nucleotides and phosphate on rat small intestine phosphate-dependent glutaminase (PDG) activity was investigated in intact mitochondria. Disruption of the integrity of mitochondria by sonication or freeze-thawing resulted in loss of enzyme activity. ADP was the strongest adenine nucleotide activator of the enzyme giving a V-max that was over 5-fold of that for AMP or ATP. The sigmoid activation curve of PDG by ADP became hyperbolic in presence ATP. ADP also lowered the K-m for glutamine and increased V-max and these effects were further enhanced by the presence of ATP. Activation of PDG by phosphate and ADP was not completely additive suggesting some antagonism between the activators. There was no clear relationship between changing ATP/ADP ratios and PDG activity in presence of a constant concentration of phosphate. However, ratios of approximately 1:4 and 4:1 gave the highest and lowest activities, respectively. The pH dependence of PDG activity was affected by phosphate concentration and results suggest that the divalent ion is the activating species. (C) 2010 Elsevier Inc. All rights reserved.
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