Heme biosynthesis pathway enzymes

The heme biosynthesis pathway is a series of eight enzymatic reactions that produce heme, an essential cofactor for oxygen transport, electron transfer, and drug metabolism (StatPearls, 2023). The pathway begins in the mitochondria with the condensation of glycine and succinyl-CoA by 5-aminolevulinate synthase (ALAS), followed by several cytoplasmic steps, and concludes back in the mitochondria with the insertion of iron into protoporphyrin IX by ferrochelatase (NIH, 2022). Deficiencies in these enzymes result in porphyrias, which manifest as either acute neurovisceral attacks or cutaneous photosensitivity due to the accumulation of porphyrin precursors (PubMed, 2017). Modern therapeutic approaches, such as the siRNA drug Givosiran, target the hepatic ALAS1 enzyme to downregulate the pathway and prevent the production of toxic intermediates (FDA, 2019). Furthermore, the pathway is critical in infectious diseases; for example, malaria parasites rely on heme metabolism, and drugs like chloroquine disrupt the sequestration of toxic heme into hemozoin (Nature, 2013). Lead poisoning also targets this pathway by inhibiting enzymes like ALAD and ferrochelatase, leading to anemia and neurological symptoms (CDC, 2021).

Other names

Porphyrin biosynthesis pathwayHeme synthesis pathwayHeme metabolic pathway

Drugs targeting the heme biosynthesis pathway function through several mechanisms: siRNA-mediated silencing of ALAS1 mRNA to reduce the production of neurotoxic precursors (e.g., Givosiran), feedback inhibition of ALAS1 via exogenous heme administration (e.g., Hemin), or the disruption of heme crystallization into non-toxic hemozoin in Plasmodium species (e.g., Chloroquine).