Sakaguchi K, Mitsui K, Hase J, Kobashi K
J Biochem. 1984 Feb;95(2):535-41. doi: 10.1093/oxfordjournals.jbchem.a134636.
Jack bean urease [EC 3.5.1.5] was modified with diazonium-1H-tetrazole (DHT). Reaction of DHT with the enzyme produced a characteristic absorption peak at 320 nm and led to complete loss of the enzymatic activity at a low concentration of DHT. Amino acid analysis of DHT-modified urease showed that only cysteine residues reacted with the reagent and other amino acid residues such as tyrosine, histidine, and lysine did not. The enzymatic activity was protected against DHT-inactivation by the addition of substrate. On the other hand, when the cysteine residues were modified with DHT, the enzyme was not converted to polymeric forms. Furthermore, the binding ability of urease with hydroxamic acid, a specific urease inhibitor, was virtually unaffected by DHT-inactivation. These results indicate that cysteine residues are specifically modified by DHT with concomitant loss of enzymatic activity and polymerization ability, but are not essential for the binding of hydroxamic acid to the enzyme.
刀豆脲酶[EC 3.5.1.5]用重氮-1H-四唑（DHT）进行了修饰。DHT与该酶反应在320 nm处产生一个特征吸收峰，并在低浓度DHT下导致酶活性完全丧失。对DHT修饰的脲酶进行氨基酸分析表明，只有半胱氨酸残基与该试剂反应，而酪氨酸、组氨酸和赖氨酸等其他氨基酸残基不反应。通过添加底物可保护酶活性免受DHT失活的影响。另一方面，当半胱氨酸残基用DHT修饰时，该酶不会转化为聚合形式。此外，脲酶与异羟肟酸（一种特异性脲酶抑制剂）的结合能力实际上不受DHT失活的影响。这些结果表明，半胱氨酸残基被DHT特异性修饰，同时酶活性和聚合能力丧失，但对于异羟肟酸与该酶的结合并非必不可少。
