Purüvaatkarboksülaasi

Purüvaatkarboksülaasi, also known as pyruvate carboxylase, is a mitochondrial enzyme that catalyzes the ATP-dependent carboxylation of pyruvate to oxaloacetate. This reaction is a crucial anaplerotic step, meaning it replenishes intermediates in the citric acid cycle. The enzyme is found in vertebrates, fungi, and some bacteria.

In mammals, purüvaatkarboksülaasi plays a vital role in gluconeogenesis, fatty acid synthesis, and the urea cycle. During gluconeogenesis, it provides oxaloacetate, a key precursor for glucose synthesis. In fatty acid synthesis, it generates acetyl-CoA from pyruvate, which is then used as a building block for fatty acids. In the urea cycle, it converts pyruvate to oxaloacetate, which is then utilized in the cycle to detoxify ammonia.

The enzyme requires biotin as a cofactor, which acts as a carrier of the carboxyl group. The reaction proceeds in two steps: first, pyruvate is carboxylated to carboxybiotin, and then the carboxyl group is transferred to pyruvate to form oxaloacetate.

Deficiencies in purüvaatkarboksülaasi can lead to serious metabolic disorders, including pyruvate carboxylase deficiency, which is a rare genetic disorder characterized by neurological abnormalities, developmental delay, and lactic acidosis. Treatment typically involves dietary management and supplementation.