Catalyzes the hydrolysis of the amide bond of N(2)-acetylated L-amino acids. Cleaves the acetyl group from N-acetyl-L-ornithine to form L-ornithine, an intermediate in L-arginine biosynthesis pathway, and a branchpoint in the synthesis of polyamines. H2O + N(2)-acetyl-L-ornithine = acetate + L-ornithine Binds 2 Zn(2+) or Co(2+) ions per subunit. Optimum pH is 7.7. Amino-acid biosynthesis; L-arginine biosynthesis; L-ornithine from N(2)-acetyl-L-ornithine (linear): step 1/1. Homodimer. Belongs to the peptidase M20A family. ArgE subfamily.