LIFE SCIENCE

Detailed explanation-1: -11.3. Pyruvate carboxylase is a biotin-dependent mitochondrial enzyme. Its activity is highest in liver and kidney, where it has a gluconeogenic role. It is also expressed widely in other organs, including brain, where it serves an anaplerotic function by providing oxaloacetate for the TCA cycle.

Detailed explanation-2: -Pyruvate carboxylase belongs to the family of biotin-dependent carboxylases and is composed of four identical subunits (∼130 kDa each) organized as a tetramer. It is present in many organisms including bacteria, fungi, plants, and animals. Pyruvate carboxylase is situated in mitochondria in most eukaryotic organisms.

Detailed explanation-3: -Pyruvate dehydrogenase and carboxylase enzymes are localized to the mitochondrial matrix and, therefore, pyruvate must be transported from the cytosol through both the outer and the inner mitochondrial membranes.

Detailed explanation-4: -Pyruvate carboxylase (PC) is a biotin-containing enzyme that catalyses the HCO3−-and MgATP-dependent carboxylation of pyruvate to form oxaloacetate. This is a very important anaplerotic reaction, replenishing oxaloacetate withdrawn from the Krebs cycle for various pivotal biochemical pathways.