ABSTRACT
Propionyl-CoA synthetase of liver and mammary gland from calf and midlactation cow was investigated. No activity of this enzyme was detected in calf mammary gland, but it was detected in calf liver. Propionyl-CoA synthetase was found in both, liver and mammary gland of the cow, although mammary gland activity was about 25% of that found in liver. The effects of pH and temperature on enzyme activity and stability were also investigated in crude extracts of liver and mammary gland tissues. The results suggest a different behaviour of the enzyme from both origins. Kinetic studies of the enzyme were also carried out, showing differences, depending on the organ, in the apparent substrate KM values.
Subject(s)
Coenzyme A Ligases/analysis , Liver/enzymology , Mammary Glands, Animal/enzymology , Acyl Coenzyme A/metabolism , Animals , Cattle , Female , Glucose/biosynthesis , Lactation/metabolism , Substrate SpecificityABSTRACT
1. Propionyl-CoA carboxylase from mid-lactation cow liver and mammary gland has been purified. 2. In both organs, the molecular mass was estimated to be approximately 450 kD, and two molecular subunits of 77 and 64 kD could be observed. 3. Physico-chemical and kinetical properties for the enzyme from both organs were similar, showing an allosteric behaviour in relation to ATP and Mg2+. 4. The presence of propionyl-CoA carboxylase in mid-lactation cow mammary gland with similar properties to the liver enzyme, could indicate the existence of a gluconeogenic metabolism in this organ exactly when a high demand of glucose for milk lactose is required.
