Kanaaneh J, Craig S P, Wang C C
Department of Pharmaceutical Chemistry, University of California San Francisco 94143-0446.
Eur J Biochem. 1994 Jul 15;223(2):595-601. doi: 10.1111/j.1432-1033.1994.tb19030.x.
The hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) of human and the parasitic trematode, Schistosoma mansoni, were expressed at high levels in transformed Escherichia coli in their native forms. Guanosine 2',3'-dialdehyde 5'-phosphate (ox-GMP) was shown to bind irreversibly to both enzymes in a time-dependent manner. This binding was stabilized by sodium borohydride reduction, suggesting that a Schiff's base is formed between the dialdehyde groups of ox-GMP and the amino group of a lysine residue in the enzymes. This linkage formation applies also to inosine 2',3'-dialdehyde 5'-phosphate but not to adenosine 2',3'-dialdehyde 5'-phosphate. GMP was found to be protective against ox-GMP inactivation and [3H]ox-GMP labeling of both HGPRTases. 5-Phosphoribosyl-1-diphosphate (PRibPP) also protects human HGPRTase against the ox-GMP inactivation and [3H]ox-GMP labeling but provides virtually no protection against the ox-GMP inactivation and labeling of the schistosomal enzyme, even though PRibPP binds to the latter with a threefold higher affinity. These results imply that PRibPP and ox-GMP compete with each other for binding to the human HGPRTase but not for binding to the schistosomal enzyme. This discrepancy could be exploited for the purpose of designing selective inhibitors of the schistosomal HGPRTase. Guanosine 2',3'-dialdehyde (ox-guanosine) is nearly as active as ox-GMP in inhibiting schistosomal HGPRTase but much less potent in inhibiting human HGPRTase, suggesting that ox-guanosine and ox-GMP may bind equally well to the parasite enzyme. PRibPP can protect human but not schistosomal HGPRTase against the inactivation by ox-guanosine. Therefore, ox-GMP and ox-guanosine must be forming Schiff's bases with the same amino acid residues in each of the two HGPRTases.
人和寄生性吸虫曼氏血吸虫的次黄嘌呤 - 鸟嘌呤磷酸核糖转移酶（HGPRTase）以天然形式在转化的大肠杆菌中高水平表达。已证明鸟苷2',3'-二醛5'-磷酸（ox - GMP）以时间依赖性方式与这两种酶不可逆结合。这种结合通过硼氢化钠还原得以稳定，表明在ox - GMP的二醛基团与酶中赖氨酸残基的氨基之间形成了席夫碱。这种连接形成也适用于肌苷2',3'-二醛5'-磷酸，但不适用于腺苷2',3'-二醛5'-磷酸。发现GMP可保护两种HGPRTase免受ox - GMP失活以及[³H]ox - GMP标记。5 - 磷酸核糖 - 1 - 二磷酸（PRibPP）也可保护人HGPRTase免受ox - GMP失活和[³H]ox - GMP标记，但对血吸虫酶的ox - GMP失活和标记几乎没有保护作用，尽管PRibPP与后者的结合亲和力高三倍。这些结果表明PRibPP和ox - GMP相互竞争与人HGPRTase的结合，但不竞争与血吸虫酶的结合。这种差异可用于设计血吸虫HGPRTase的选择性抑制剂。鸟苷2',3'-二醛（ox - 鸟苷）在抑制血吸虫HGPRTase方面几乎与ox - GMP一样有效，但在抑制人HGPRTase方面效力要低得多，这表明ox - 鸟苷和ox - GMP可能与寄生虫酶的结合效果相当。PRibPP可保护人HGPRTase免受ox - 鸟苷的失活作用，但不能保护血吸虫HGPRTase。因此，ox - GMP和ox - 鸟苷必定在两种HGPRTase中的每一种中与相同的氨基酸残基形成席夫碱。
