Aspartate transcarbamylase (ATCase)

Aspartate transcarbamylase (ATCase) is a key allosteric enzyme that catalyzes the first committed step in the biosynthesis of pyrimidine nucleotides. This reaction is essential for the production of DNA and RNA building blocks in cells. ATCase catalyzes the condensation of L-aspartate and carbamoyl phosphate to form N-carbamoyl-L-aspartate and inorganic phosphate. The enzyme’s activity is tightly regulated by feedback inhibition from cytidine triphosphate (CTP) and activated by ATP. ATCase is a dodecamer composed of 12 subunits: six catalytic chains arranged into two trimers at the core, surrounded by three regulatory dimers. It exists in equilibrium between two conformational states: Tense (T) and Relaxed (R). The transition between these states underlies both cooperativity among active sites and allosteric regulation by nucleotides.

Other names

Aspartate carbamoyltransferase

Inhibition of enzymatic activity; allosteric modulation