 In bacteria, it also produces more complex substances such as cofactor F430 and cobalamin (vitamin B12).The pathway is initiated by the synthesis of δ-aminolevulinic acid (dALA or δALA) from the amino acid glycine and succinyl-CoA from the citric acid cycle (Krebs cycle).The rate-limiting enzyme responsible for this reaction, "ALA synthase", is negatively regulated by glucose and heme concentration.