J

Carbamoyl phosphate

Aspartate

/V-Carbamoylaspartate

5-Aminoimidazole-4-carboxylic acid ribonucleotide

Aspartate

5-Aminoimidazole-4-A/-succinocarboxamide ribonucleotide i

Dihydroorotate i

Orotate i

Orotidylate

Uridyl ate (UMP)

Fig. 4.7. Biosynthesis of pyrimidines. Enzymes: 1, carbamoyl phosphate synthetase; 2, aspartate transcarbamoyl 3S61 3, dihydroorotase; 4, dihydroorotate dehydrogenase; 5, orotate phosphoribosyltransferase; 6, orotidylate decarboxyl 3S6 •

requires pyridoxal phosphate as cofactor (Stabler et ai, 1996).

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