Chauthaiwale J, Rao M
Division of Biochemical Sciences, National Chemical Laboratory, Pune, India.
Biochem Biophys Res Commun. 1993 Mar 31;191(3):922-7. doi: 10.1006/bbrc.1993.1305.
Experimental evidence for the specific interaction of guanidine hydrochloride with the carboxyl group of xylanase has been presented for the first time. Guanidine hydrochloride (0.1 M) inactivated the xylanase from alkalothermophilic Bacillus sp. to 50% without affecting the conformation of the protein as determined by the fluorometric profile. The kinetic analysis indicated a competitive type of inhibition and a requirement of 1.4 molecules of guanidine hydrochloride per molecule of the enzyme for inhibition. Maximum inhibition occurred at the pH which is optimum for the enzyme activity. The reaction of guanidine hydrochloride with the enzyme prior to modification by Woodward's Reagent K, a specific inhibitor of the carboxyl group, made it inaccessible for modification as indicated by absorbance data at 340 nm. Urea, sodium dodecyl sulphate, LiCl, KCl and NaCl at 0.1 M concentration each had negligible effect on the enzyme activity.
首次提出了盐酸胍与木聚糖酶羧基特异性相互作用的实验证据。0.1 M盐酸胍使嗜碱嗜热芽孢杆菌的木聚糖酶失活50%，同时通过荧光光谱分析确定其不会影响蛋白质的构象。动力学分析表明这是一种竞争性抑制类型，每分子酶抑制需要1.4分子盐酸胍。最大抑制作用发生在酶活性最佳的pH值。在用羧基特异性抑制剂伍德沃德试剂K修饰之前，盐酸胍与酶的反应使得其无法被修饰，这可通过340 nm处的吸光度数据得到证明。浓度均为0.1 M的尿素、十二烷基硫酸钠、LiCl、KCl和NaCl对酶活性的影响可忽略不计。
