Regulation of Pyrimidine Biosynthesis in Intact Cells of Cucurbita pepo1

AUTOR(ES)

Lovatt, Carol J.

RESUMO

The occurrence of the complete orotic acid pathway for the biosynthesis de novo of pyrimidine nucleotides was demonstrated in the intact cells of roots excised from summer squash (Cucurbita pepo L. cv. Early Prolific Straightneck). Evidence that the biosynthesis of pyrimidine nucleotides proceeds via the orotate pathway in C. pepo included: (a) demonstration of the incorporation of [14C]NaHCO3, [14C]carbamylaspartate, and [14C]orotic acid into uridine nucleotides; (b) the isolation of [14C]orotic acid when [14C]NaHCO3 and [14C]carbamylaspartate were used as precursors; (c) the observation that 6-azauridine, a known inhibitor of the pathway, blocked the incorporation of early precursors into uridine nucleotides while causing a concomitant accumulation of orotic acid; and (d) demonstration of the activities of the component enzymes of the orotate pathway in assays employing cell-free extracts.

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