Enables 5-aminolevulinate synthase activity. Involved in erythrocyte differentiation; heme biosynthetic process; and hemoglobin biosynthetic process. Acts upstream of or within cellular iron ion homeostasis. Located in mitochondrion. Is expressed in several structures, including alimentary system; brain; genitourinary system; hemolymphoid system gland; and liver and biliary system. Human ortholog(s) of this gene implicated in cutaneous porphyria; erythropoietic protoporphyria; hemochromatosis; sideroblastic anemia; and sideroblastic anemia 1. Orthologous to human ALAS2 (5'-aminolevulinate synthase 2). [provided by Alliance of Genome Resources, Apr 2022]