Evolution of pyruvate carboxylase and other biotin containing enzymes in developing rat liver and kidney

The evolution of pyruvate carboxylase has been studied in rat liver and kid ney during perinatal development. The pyruvate carboxylase activity, amount of enzyme and mRNA levels have been assayed from 2 days before delivery to weaning. In liver, there is a peak of activity and amount of enzyme 24 h b efore delivery and 2 peaks, at 12 h and 6 days, after parturition. The tran scription of the enzyme gene followed a similar pattern, with mRNA peaks pr eceding those of activity and amount of enzyme. However, in kidney, pyruvat e carboxylase activity, amount and mRNA remain low until weaning. These res ults confirm the limited role of renal gluconeogenesis during the perinatal development. Since all carboxylases contain biotin as prosthetic group, th e biotinylation of pyruvate carboxylase during the perinatal period was inv estigated by western-blot using streptavidin-biotin peroxidase. In the mito chondrial samples from liver and kidney, all the pyruvate carboxylase detec ted was fully biotinylated, indicating an early development of the holocarb oxylase synthetase activity in the perinatal period. This Western-blot tech nique also allowed us the detection of other biotin-enzymes based on their molecular weight. In liver, during the perinatal development propionyl-coA and 3-methyl-crotonyl-coA carboxylases followed a pattern of induction simi lar to pyruvate carboxylase. In kidney, the expression of mitochondrial car boxylases was lower compared to liver and propionyl-coA carboxylase was not detected during the studied period.