Heme synthesis pathway enzymes

The heme synthesis pathway enzymes comprise a series of eight catalytic proteins responsible for the de novo biosynthesis of heme, a vital prosthetic group for oxygen transport (hemoglobin), electron transfer (cytochromes), and various redox reactions [1.3.1, 1.4.1]. The pathway is partitioned between the mitochondria and the cytosol, beginning with the condensation of glycine and succinyl-CoA by 5-aminolevulinate synthase (ALAS) and concluding with the insertion of ferrous iron into protoporphyrin IX by ferrochelatase (FECH) [1.3.1, 1.4.2]. Genetic mutations in any of these enzymes lead to porphyrias, a group of rare metabolic disorders characterized by the accumulation of toxic porphyrin intermediates [1.4.4, 1.4.5]. Therapeutic intervention often involves modulating the pathway's activity; for instance, Givosiran is an RNAi therapy that reduces ALAS1 levels to prevent the buildup of neurotoxic precursors in acute hepatic porphyria [1.3.1]. Additionally, the pathway is a target for environmental toxins like lead, which inhibits ALAD and FECH, and is utilized in photodynamic therapy where exogenous ALA is used to generate photosensitizing protoporphyrin IX in malignant tissues [1.5.1, 1.5.2]. Regulation of these enzymes is tissue-specific, with ALAS1 serving as the rate-limiting step in the liver and ALAS2 in erythroid cells [1.3.2, 1.3.3].

Other names

Heme biosynthetic pathway enzymesPorphyrin synthesis pathway enzymesHeme pathway enzymes

Inhibition of rate-limiting enzymes (e.g., ALAS1) to reduce toxic intermediate accumulation, supplementation of pathway products for feedback inhibition, or administration of precursors for photodynamic therapy.