PYRIMIDINE BIOSYNTHESIS . PYRIMIDINE BIOSYNTHESIS

What is nucleotides? Nucleotides are organic molecules that serve as the monomers, or subunits of nucleic acids like DNA and RNA .

And nucleosides:molecule without phosphate group The nitrogenous bases are derivatives of two parent compounds ,purine and pyrimidine.

Pyrimidine nucleotide structure are.. UMP CMP TMP

PYRIMIDENE BIOSYNTHESIS

CMP foamed from UMP by the action of cytidylate synthetase Synthesis of CMP CMP foamed from UMP by the action of cytidylate synthetase

Synthesis of deoxyribonucleotide

. Deoxyribonucleotide, derived from the ribonucleotides by direct reduction at the 2'_ carbon atom of the D-ribose to foam the 2'-deoxy derivative. 1. This reaction is catalyzed by ribonucleotide reductase. This reaction required H atom carry by thioredoxin. Its oxidized foam is reduced by NADPH in a reaction catalyzed by thioredoxin reductase.

. The second source of reducing equivalents for ribonucleotide reductase is glutathione(GSH).

thymidylate is derived fron dCDP and dUMP

. DNA contain thymine rather than uracil,de nevo pathway to thymine involve only deoxtribonucleotides The precursor of thymidylate is dUMP. dUMP begins with the formation of dUTP. The conversion of dUMP to dTMP is catalyzed by thymidylate synthase.

THYMIDYLATE SYNTHESIS

SALVAGE PATHWAY A salvage pathway is a pathway in which nucleotides are synthesised from intermediates in the degrative pathway for nucleotides. .salvage pathway consist of single reaction catalyzed by adenosine phosphoribosyltransferase. Adenine+PRPP AMP+PPi

Lesch-Nyhan syndrome Free guanine and hypoxanthine are salvaged by hypixanthine-guanine phosphoribosyltransferase. A lack of hypoxanthine-guanine phosphoribosyltransferase activity, seen in male children , result in a bizarre set of symptoms called Leach-Nyhan syndrome.

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