Rate limiting step in heme synthesis is catalyzed by-

Ans. is 'b' i.e., ALA synthase Synthesis of hemeo Heme synthesis takes place in all cells, but occurs to greatest extent in bone marrow and liver,o The first step in the synthesis of heme is the condensation of glycine and succinyl Co-A to form d-aminolevulinic acid (d-ALA), which occurs in mitochondria.o This reaction is catalyzed by d-ALA synthase which requires pyridoxal phosphate (PLP) as cofactor,o This is the rate limiting step in heme synthesis.o Heme is then combined with protein component (e.g. globin) to form hemoproten (e.g. hemoglobin).