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. glycine + H(+) + succinyl-CoA = 5-aminolevulinate + CO2 + CoA Activity increases about 2-fold over 72 h of hypoxia compared with normoxia (PubMed:16234850). Activity increases in the presence of phenobarbital, chenodeoxycholic and NR1H4/FXR-specific agonist GW4064 (PubMed:17975826). Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; 5-aminolevulinate from glycine: step 1/1. Homodimer (By similarity). Interacts (hydroxylated form) with VHL (PubMed:16234850). Localizes to the matrix side of the mitochondrion inner membrane. Up-regulated by bile acids; chenodeoxycholic acid, ursodeoxycholic acid and lithocholic acid and by the NR1H4/FXR-specific agonist GW4064. In normoxia, is hydroxylated at Pro-576, promoting interaction with VHL, initiating ubiquitination and subsequent degradation via the proteasome. Ubiquitinated; in normoxia following hydroxylation and interaction with VHL, leading to its subsequent degradation via the proteasome. Belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family.