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 Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; 5-aminolevulinate from glycine: step 1/1. Homodimer (By similarity). Interacts (hydroxylated form) with VHL (By similarity). Localizes to the matrix side of the mitochondrion inner membrane. In normoxia, is hydroxylated at Pro-578, 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.