Crystal Structure and Functional Characterization of Acetylornithine Aminotransferase from Corynebacterium glutamicum .

The amino acids l-arginine and l-ornithine are widely used in animal feed and as health supplements and pharmaceutical compounds. In arginine biosynthesis, acetylornithine aminotransferase (AcOAT) uses pyridoxal-5'-phosphate (PLP) as a cofactor for amino group transfer. Here, we determined the crystal structures of the apo and PLP complex forms of AcOAT from Corynebacterium glutamicum ( Cg AcOAT). Our structural observations revealed that Cg AcOAT undergoes an order-to-disorder conformational change upon binding with PLP. Additionally, we observed that unlike other AcOATs, Cg AcOAT exists as a tetramer. Subsequently, we identified the key residues involved in PLP and substrate binding based on structural analysis and site-directed mutagenesis. This study might provide structural insights on Cg AcOAT, which can be utilized for the development of improved l-arginine production enzymes.