pyruvate carboxylase /pī′ro̅o̅·vāt kär·bok′sə·lās/ , an enzyme that catalyzes the irreversible carboxylation of pyruvate, a reaction necessary for gluconeogenesis from lactate or amino acids forming pyruvate and also providing four-carbon compounds for the citric acid cycle. The enzyme is a mitochondrial protein occurring in liver but not in muscle. Deficiency of the enzyme, an autosomal-recessive trait, causes severe psychomotor slowing and lactic acidosis in infants. There is a particularly severe, rapidly fatal form in which hyperammonemia, citrullinemia, and an excess of lysine in the blood are also present.
