3-amino-5-hydroxybenzoic acid synthase family (AHBA_syn). AHBA_syn family belongs to pyridoxal phosphate (PLP)-dependent aspartate aminotransferase superfamily (fold I). The members of this CD are involved in various biosynthetic pathways for secondary metabolites. Some well studied proteins in this CD are AHBA_synthase, protein product of pleiotropic regulatory gene degT, Arnb aminotransferase and pilin glycosylation protein. The prototype of this family, the AHBA_synthase, is a dimeric PLP dependent enzyme. AHBA_syn is the terminal enzyme of 3-amino-5-hydroxybenzoic acid (AHBA) formation which is involved in the biosynthesis of ansamycin antibiotics, including rifamycin B. Some members of this CD are involved in 4-amino-6-deoxy-monosaccharide D-perosamine synthesis. Perosamine is an important element in the glycosylation of several cell products, such as antibiotics and lipopolysaccharides of gram-positive and gram-negative bacteria. The pilin glycosylation protein encoded by gene pglA, is a galactosyltransferase involved in pilin glycosylation. Additionally, this CD consists of ArnB (PmrH) aminotransferase, a 4-amino-4-deoxy-L-arabinose lipopolysaccharide-modifying enzyme. This CD also consists of several predicted pyridoxal phosphate-dependent enzymes apparently involved in regulation of cell wall biogenesis. The catalytic lysine which is present in all characterized PLP dependent enzymes is replaced by histidine in some members of this CD.