Question

Do purine and pyrimidine catabolism produce ATP?

Answer 1

There is no synthesis of ATP during catabolism of purine and pyrimidine. ATP itself contains a purine (Adenine) which is either recycled by salvage pathway (AMP synthesis) or broken down to yield uric acid.

The Purine catabolism involves following steps

Removal of phosphate by nucleotidases

The nucleoside (adenosine) undergoes deamination and subsequent hydrolysis yields hypoxanthine by the action of deaminases and nucleosidase.

Latter on hypoxanthine is converted to uric acid and excreted out

Free purines also undergo through an alternate salvage pathway during which new nucleotides are synthesized by catabolic intermediates by the enzyme phosphoribosyltransferases. Here AMP can be synthesized by joining PhosphoRibosylPyroPhosphate and adenine by the action of adenine phosphoribosyl transferase. But ATP is not synthesized. For ATP synthesis AMP goes to energy yielding pathways (Glycolysis or krebs cycle) where different substrated with high phosphoryl group transferring potential transfer phosphates and make ADP and ATP from AMP.

Pyrimidine catabolism

Pyrimidines also undergo salvage pathway inorder to synthesize new nucleotides (for example UMP ). Alternatively they are converted to malonyl coA and beta alanine. Malonyl coA can latter take part in suynthesis of fatty acids, Remaining carbons can enter into TCA cycle as reaction intermediates such as acetyl coA and succinyl coA and may produce ATP indirectly. But there is no direct synthesis of ATP during pyrimidine catabolism as TTP,GTP and CTP are being broken doen here/.

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