Aminolevulinic Acid Synthase and Heme Synthesis: Understanding the Rate-Limiting Step and Regulation Factors.

Reaction 1 of Heme synthesis

location: mitochondiran matrixenzyme: delta aminolevulinate synthase (ALAS)condensation reaction between succinyl CoA and glycine to form delta aminolevulinate (ALA)THIS IS THE LIMITING STEP OF HEME SYNTHESIS gives of CoA and CO2highly regulated: increased levels of heme create negative feedback and reduces transcription and translation of delta aminolevulinate synthase and decreases its transportation into the mitochondrian

The first reaction of heme synthesis is the condensation of glycine and succinyl-CoA catalyzed by the enzyme aminolevulinic acid synthase (ALAS). The reaction takes place in the mitochondria of erythroid cells and involves the transfer of a methylene group from the carbonyl of succinyl-CoA to the amino group of glycine. This results in the formation of aminolevulinic acid (ALA), a four-carbon compound that serves as the precursor for the synthesis of porphyrins.

This reaction is the rate-limiting step of heme synthesis and is regulated by various factors, including intracellular iron levels and the availability of succinyl-CoA. ALAS is also subject to feedback inhibition by heme, which acts as a negative regulator of its own synthesis. The second reaction involves the formation of porphobilinogen from two molecules of ALA, catalyzed by the enzyme ALA dehydratase.

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