in the presence of 0.5 millimolar allopurinol ( 4-hydroxypyrazolo [ 3,4-d ] pyrimidine ) , an inhibitor of nad : xanthine oxidoreductase ( ec 1.2.3.2 ) , intact attached nodules of cowpea ( vigna unguiculata l. walp . cv vita 3 ) formed [ ( 15 ) n ] xanthine from ( 15 ) n ( 2 ) at rates equivalent to those of ureide synthesis , confirming the direct assimilation of fixed nitrogen into purines .
C0002144
allopurinol
C0034140
purines