Transaminase converting glutamate 1-semialdehyde (GSA) to 5-aminolevulinate (ALA). Involved in the biosynthesis of tetrapyrroles. (S)-4-amino-5-oxopentanoate = 5-aminolevulinate Can use both pyridoxamine 5'-phosphate (PMP) and pyridoxal 5'-phosphate (PLP) as cofactors. A relatively lower peak at 418 nm is also observed. At pH 7.5. Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; 5-aminolevulinate from L-glutamyl-tRNA(Glu): step 2/2. Porphyrin-containing compound metabolism; chlorophyll biosynthesis. Homodimer. Present in all tissues tested. By light. In etiolated seedlings, initial expression is reduced but after further illumination, levels steadily increase. Suppresses partially the ENF1 disruption pleiotropic developmental phenotypes. Belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family. HemL subfamily.