δ-aminolevulinate synthase
5-aminolevulinate synthase, unspecific | ||
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Ribbon model (tetramer) of the ALAS of Rhodobacter , according to PDB 2BWN | ||
Properties of human protein | ||
Mass / length primary structure | 584 amino acids | |
Secondary to quaternary structure | Homodimer | |
Cofactor | Pyridoxal phosphate | |
Isoforms | 2 | |
Identifier | ||
Gene name | ALAS1 | |
External IDs | ||
Enzyme classification | ||
EC, category | 2.3.1.37 , transferase | |
Substrate | Succinyl-CoA + glycine | |
Products | 5-aminolevulinate + CoA + CO 2 | |
Occurrence | ||
Homology family | ALAS | |
Parent taxon | Creature |
The δ-aminolevulinate synthase ( δ-ALAS ) is a mitochondrial enzyme that is found in hepatocytes and erythroblasts . There are two isoenzymes , one that occurs ubiquitously (gene: ALAS1 ) and one that is specific for erythroblasts (gene: ALAS2 ). The enzyme catalyzes the reaction of succinyl-CoA from the citric acid cycle with the amino acid glycine to form δ-aminolevulinate with the elimination of CO 2 . This reaction is the rate-limiting step in heme biosynthesis . The reaction is dependent on pyridoxal phosphate . The δ-aminolevulinate synthase is inhibited by heavy metals such as lead and by heme itself as the end product of the heme biosynthetic pathway.
A defect in the ALAS2 gene leads to a (very rare) chromosome X -linked sideroblastic anemia . This leads to iron accumulation in the mitochondria of the bone marrow cells.