Turnover of adenosine triphosphatase from rat liver mitochondria. Effect of high-protein and low-protein diets.
The half-life of mitochondrial adenosine triphosphatase and the relative rate constants of protein degradation for several fractions of rat liver have been measured by the double-isotope technique. It has been shown that the apparent turnover rates of some mitochondrial enzymes, far apart in size, such as carbamoyl phosphate synthetase, glutamate dehydrogenase and malate dehydrogenase, are not related to molecular weight or to size of subunits. In view of the possibility that mitochondrial proteins are degraded by different mechanisms, it was of interest to determine the half-life of a protein tightly bound to the inner membrane such as adenosine triphosphatase. The rate constants of degradation for rats fed a basal diet and injected at three-day intervals with isotopic leucine were: homogenate, kd = 0.195 days-1; mitochondria, kd = 0.135 days-1; cytosol, kd = 0.140 days-1; microsomes, kd = 0.28 days-1; ATPase, kd = 0.275 days-1. The rate constants of the cellular fractions of liver of rats fed a high protein diet did not change or showed a small increase, compared with those of animals fed the basal diet, while those from rats on the protein-free diet showed a decrease. The rate constant for adenosine triphosphatase showed an increase with high-protein and a decrease with protein-free diet. A procedure for the purification of ATPase from a single liver of a rat is described.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002250:Carbon Radioisotopes; D004044:Dietary Proteins / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008930:Mitochondria, Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium
D002250:Carbon Radioisotopes; D004044:Dietary Proteins; D014316:Tritium; D000251:Adenosine Triphosphatases