Fig. 1
From: Characterizing selective pressures on the pathway for de novo biosynthesis of pyrimidines in yeast
a. Schematic presentation of the de novo pyrimidine biosynthesis and its feedback regulation in S. cerevisiae. Red arrows show downregulation of enzymatic activity and gene expression, respectively. Green arrows show upregulation of gene expression. Enzymatic activities are represented in the boxes, with S. cerevisiae gene names above them: Carbamoyl-phosphate synthetase (CPSase, URA2) and aspartate transcarbamylase (ATCase, URA2), dihydroorotase (DHOase, URA4), dihydroorotate dehydrogenase (DHODH, URA1), orotate phosphoribosyltransferase (OPRtase, URA5 and URA10), orotidine-5’-phosphate decarboxylase (ODCase, URA3), uridylate kinase (UMPK, URA6), nucleoside diphosphate kinase (UDPK, YNK1), CTP synthase (CTPS, URA7 and URA8). The free intermediates of the pathway are N-carbamoyl-aspartate (CA_asp), dihydroorotate (DHO), orotate (OA), orotidylate (OMP). b. Comparison of the de novo pyrimidine biosynthesis in selected organisms. Figure modified after [13, 14, 18]