Lewis N J, Hurt P, Sealy-Lewis H M, Scazzocchio C
Eur J Biochem. 1978 Nov 2;91(1):311-6. doi: 10.1111/j.1432-1033.1978.tb20967.x.
The purine hydroxylases I and II of Aspergillus nidulans [previously called xanthine dehydrogenases I and II: Scazzocchio, Holl and Foguelman, Eur. J. Biochem. 36, 428--445 (1973)] have been studied in crude extracts. The two enzymes differ in their substrate specificities, purine hydroxylase II being able to accept nicotinate as a substrate and unable to hydroxylate xanthine. The kinetics of inhibition with allopurinol and oxypurinol are also different, the two analogues being pseudo-irreversible inhibitors of purine hydroxylase I, while allopurinol is a competitive inhibitor of purine hydroxylase II and oxypurinol shows anti-competitive inhibition. Differences in electro-phoretic mobility and molecular size are also shown. We have failed to show the formation of hybrid purine hydroxylase I/II molecules. While a common evolutionary origin of the purine hydroxylases could be postulated, the data reveal a considerable divergence.
构巢曲霉的嘌呤羟化酶I和II（以前称为黄嘌呤脱氢酶I和II：斯卡佐基奥、霍尔和福格尔曼，《欧洲生物化学杂志》36，428 - 445（1973））已在粗提取物中进行了研究。这两种酶的底物特异性不同，嘌呤羟化酶II能够接受烟酸作为底物，而不能使黄嘌呤羟化。别嘌呤醇和氧嘌呤醇的抑制动力学也不同，这两种类似物是嘌呤羟化酶I的假不可逆抑制剂，而别嘌呤醇是嘌呤羟化酶II的竞争性抑制剂，氧嘌呤醇表现出反竞争性抑制。还显示了电泳迁移率和分子大小的差异。我们未能证明杂合嘌呤羟化酶I/II分子的形成。虽然可以假定嘌呤羟化酶有共同的进化起源，但数据显示出相当大的差异。
