This family of proteins, for which ornithine aminotransferases form an outgroup, consists mostly of proteins designated acetylornithine aminotransferase. However, the two very closely related members from Escherichia coli are assigned different enzymatic activities. One is acetylornithine aminotransferase (EC: 2.6.1.11), ArgD, an enzyme of arginine biosynthesis, while another is succinylornithine aminotransferase, an enzyme of the arginine succinyltransferase pathway, an ammonia-generating pathway of arginine catabolism [PMID:9696779]. Members of this family may also act on ornithine, like ornithine aminotransferase (EC: 2.6.1.13) [PMID:2199330] and on succinyldiaminopimelate, like N-succinyldiaminopmelate-aminotransferase (EC: 2.6.1.17, DapC, an enzyme of lysine biosynthesis) [PMID:10074354].