Catalyzes the biosynthesis of ornithine by transacetylation between N(2)-acetylornithine and glutamate. It can also use L-arginine, L-glutamine and L-lysine as acetyl acceptors. L-glutamate + N(2)-acetyl-L-ornithine = L-ornithine + N-acetyl-L-glutamate Optimum pH is between 7.5-8. Antibiotic biosynthesis; clavulanate biosynthesis. Heterotetramer of two alpha and two beta chains. The role of this protein is probably directed towards producing increased intracellular concentrations of arginine for clavam biosynthesis, rather than primary metabolism. Belongs to the ArgJ family.