pyrimidine biosynthetic pathway de novo pyrimidine biosynthetic pathway 'de novo' pyrimidine nucleobase biosynthetic process 2011-06-03T03:58:08Z In the de novo biosynthetic pathway, pyrimidines are synthesized from simple precursors. Six reactions carried out by three enzymes in higher eukaryotes result in the formation of UMP, the precursor of all other pyrimidine nucleotides. PW:0000862 pathway vpetri