Purification by affinity chromatography of thermostable glyceraldehyde 3-phosphate dehydrogenase from Thermus aquaticus.

activities of the key enzymes of gluconeogenesis in the liver and kidney of the foetal guinea pig have been followed. The foetal guinea pigs used had a gestational age of 68-72 days. Pyruvate carboxylase was present at very low activities in the kidney of the foetus and neonatal animal and also in the foetal liver until day 50, when it increased in activity to reach a value by day 60 of more than twice the maternal liver value. There was a rapid postnatal fall in activity. The foetal liver enzyme was largely mitochondrial, required acetyl-CoA for activity and, like the adult liver enzyme, had a Km for pyruvate of approx. 0.7mM. Unlike the adult liver, most of the phosphopyruvate carboxylase was particulate, and the solublefraction enzyme of the foetal liver had the properties of the particulate enzyme of the adult and foetal liver. Particulate enzyme, which was largely mitochondrial, was present in significant amounts from day 35, and by day 65 its activity was approximately threefold greater in the foetal liver than the adult liver. In both the liver and the kidney soluble-enzyme activity was low during foetal life but showed a large rise during the first 2 days after birth. Fructose 1,6-diphosphatase was present in low activity in the foetal liver and kidney until day 40, when its activity rapidly rose so that by day 45 it was just below the maternal enzyme activities. Foetal liver and maternal liver enzymes had similar properties, although the foetal liver enzyme was more sensitive to AMP and substrate inhibition and had a Km for fructose 1,6-diphosphate of 1 uM. The changes in the activities of glucose 6-phosphatase were very similar to those for fructose 1,6diphosphatase. In the foetal tissues the enzyme reached an activity of about half that found in the adult, had a Km of lOmnim and was inhibited by glucose.