The function of Ensembl gene identifier ENSG00000023330 (ALAS1, 5'-aminolevulinate synthase 1) is as follows. Catalyzes the pyridoxal 5'-phosphate (PLP)-dependent condensation of succinyl-CoA and glycine to form aminolevulinic acid (ALA), with CoA and CO2 as by-products. {ECO:0000269|PubMed:16234850, ECO:0000269|PubMed:17975826}.