tetrapyrrole biosynthetic process

Definition

Target type: biologicalprocess

The chemical reactions and pathways leading to the formation of tetrapyrroles, natural pigments containing four pyrrole rings joined by one-carbon units linking position 2 of one pyrrole ring to position 5 of the next. [GOC:mah]

Tetrapyrrole biosynthesis is a fundamental metabolic pathway that produces essential porphyrin molecules, including heme, chlorophyll, and cobalamin (vitamin B12). These porphyrins play crucial roles in various biological processes, such as oxygen transport, photosynthesis, and cellular respiration. The pathway involves a series of enzymatic reactions that convert simple precursors into complex tetrapyrrole structures.

The process begins with the condensation of succinyl CoA from the citric acid cycle and the amino acid glycine, catalyzed by the enzyme delta-aminolevulinate synthase (ALAS). This reaction forms delta-aminolevulinate (ALA), the first committed intermediate in tetrapyrrole biosynthesis.

Two molecules of ALA are then combined by the enzyme porphobilinogen deaminase (also known as hydroxymethylbilane synthase) to produce the monopyrrole derivative porphobilinogen. Four molecules of porphobilinogen are then assembled into a linear tetrapyrrole chain, called protoporphyrinogen IX, through a series of complex enzymatic reactions. This step is catalyzed by the enzymes porphobilinogen deaminase, protoporphyrinogen oxidase, and coproporphyrinogen oxidase.

Finally, the protoporphyrinogen IX molecule is oxidized to protoporphyrin IX. This step is catalyzed by the enzyme protoporphyrinogen oxidase. Protoporphyrin IX is the precursor to heme, chlorophyll, and other porphyrins. Heme is the iron-containing molecule that is essential for oxygen transport in red blood cells. Chlorophyll is the pigment that absorbs light energy in photosynthesis. Cobalamin (vitamin B12) is a complex cofactor required for various enzymatic reactions, including DNA synthesis.

Tetrapyrrole biosynthesis is a highly regulated process that is essential for life. The enzymes involved in this pathway are subject to a variety of regulatory mechanisms, including feedback inhibition, gene expression, and protein degradation. Disruptions in tetrapyrrole biosynthesis can lead to a variety of human diseases, including porphyrias and anemia.

This detailed description outlines the key steps and enzymes involved in tetrapyrrole biosynthesis, emphasizing its significance in various biological functions and the consequences of disruptions in this critical pathway.'
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Proteins (1)

Compounds (5)