Pyrimidine Catabolism

Pyrimidine Catabolism

Pyrimidine Catabolism pt 1

In contrast to purines, pyrimidines undergo ring cleavage and the usual end products of catabolism are beta-amino acids plus ammonia and carbon dioxide. Pyrimidines from nucleic acids or the energy pool are acted upon by nucleotidases and pyrimidine nucleoside phosphorylase to yield the free bases. The 4-amino group of both cytosine and 5-methyl cytosine is released as ammonia.

Ring Cleavage

In order for the rings to be cleaved, they must first be reduced by NADPH. Atoms 2 and 3 of both rings are released as ammonia and carbon dioxide. The rest of the ring is left as a beta-amino acid. Beta-amino isobutyrate from thymine or 5-methyl cytosine is largely excreted. Beta-alanine from cytosine or uracil may either be excreted or incorporated into the brain and muscle dipeptides, carnosine (his-beta-ala) or anserine (methyl his-beta-ala).

General Comments

Pyrimidine Catabolism pt 2

Purine and pyrimidine bases which are not degraded are recycled - i.e. reincorporated into nucleotides. This recycling, however, is not sufficient to meet total body requirements and so some de novo synthesis is essential. There are definite tissue differences in the ability to carry out de novo synthesis. De novo synthesis of purines is most active in liver. Non-hepatic tissues generally have limited or even no de novo synthesis. Pyrimidine synthesis occurs in a variety of tissues. For purines, especially, non-hepatic tissues rely heavily on preformed bases - those salvaged from their own intracellular turnover supplemented by bases synthesized in the liver and delivered to tissues via the blood.

"Salvage" of purines is reasonable in most cells because xanthine oxidase, the key enzyme in taking the purines all of the way to uric acid, is significantly active only in liver and intestine. The bases generated by turnover in non-hepatic tissues are not readily degraded to uric acid in those tissues and, therefore, are available for salvage. The liver probably does less salvage but is very active in de novo synthesis - not so much for itself but to help supply the peripheral tissues.

De novo synthesis of both purine and pyrimidine nucleotides occurs from readily available components.

Reprint Permission Given to Gout-Aware All Articles written & supplied by

Dr Carol .N. Angsatdt Ph.D Department of Biomedical Sciences Allegheny University of Health Sciences

Gout Treatments

Purine Metabolism

Pyrimidine Catabolism

information about fitness and healtcare. Daily Updated News and Reports about Fitness and HealthCare. Also featuring Products from Companies in Health Care, Weightloss and Body Fitness. http://fitness.pacificherald.com

Recent Articles

  1. Sambazon Acai original for gout

    Sep 04, 17 04:24 PM

    I have gout and I often drink Sambazon Acai original organic drink for about 3 days and my pain is gone. Better than any medication and pain killers. But

    Read More

  2. What is Gout

    Aug 26, 17 02:48 AM

    What is Gout - Gout, the oldest and most common form of Arthritis. The latest information on causes and symptoms of Gout, remedies and facts.

    Read More

  3. 1st time hopefully the last

    Aug 21, 17 03:58 AM

    I'm a first timer with gout and I wonder if moscato caused it. I tried it for the first time on my birthday and a few days later I had gout. Happy birthday!!

    Read More