Waheed A, Van Etten R L
Biochim Biophys Acta. 1985 Sep 20;831(1):67-73. doi: 10.1016/0167-4838(85)90150-5.
Rabbit liver arylsulfatase A (aryl-sulfate sulfhydrolase, EC 3.1.6.1) monomers of 130 kDa contain two free sulfhydryl groups as determined by spectrophotometric titration using 5,5'-dithiobis(2-nitrobenzoate) and by labeling with the fluorescent probe 5-(iodoacetamidoethyl)aminonaphthalene-1-sulfonic acid. Fluorescence quenching data indicate that the reactive sulfhydryl is present in proximity to one or more tryptophan residues. Chemical modification of the sulfhydryl groups does not alter the distinctive pH-dependent aggregation property of the arylsulfatase A. The free sulfhydryls of the enzyme react with numerous sulfhydryl reagents. Based on the reactions of iodoacetic acid, methyl methanethiosulfonate, 5,5'-dithiobis(2-nitrobenzoate) and 5-(iodoacetamidoethyl)aminonaphthalene-1-sulfonic acid with the sulfhydryl groups of arylsulfatase A, it is concluded that free sulfhydryls are not essential for the enzyme activity. In contrast, the observed inactivation of the enzyme by p-hydroxymercuribenzoate or p-hydroxymercuriphenylsulfonate is probably due to a modification of a histidine residue, consistent with previous reports that histidine is near the active site of arylsulfatase A. p-Hydroxymercuribenzoate and p-hydroxymercuriphenylsulfonate are able to react both with cysteine and with histidine residues of the protein molecule.
兔肝芳基硫酸酯酶A（芳基硫酸硫酸水解酶，EC 3.1.6.1）的130 kDa单体含有两个游离巯基，这是通过使用5,5'-二硫代双（2-硝基苯甲酸）进行分光光度滴定以及用荧光探针5-（碘乙酰氨基乙基）氨基萘-1-磺酸标记来确定的。荧光猝灭数据表明，反应性巯基存在于一个或多个色氨酸残基附近。巯基的化学修饰不会改变芳基硫酸酯酶A独特的pH依赖性聚集特性。该酶的游离巯基与多种巯基试剂反应。基于碘乙酸、甲硫基磺酸甲酯、5,5'-二硫代双（2-硝基苯甲酸）和5-（碘乙酰氨基乙基）氨基萘-1-磺酸与芳基硫酸酯酶A巯基的反应，得出游离巯基对酶活性并非必需的结论。相比之下，观察到对羟基汞苯甲酸或对羟基汞苯磺酸使该酶失活，可能是由于组氨酸残基的修饰，这与之前关于组氨酸靠近芳基硫酸酯酶A活性位点的报道一致。对羟基汞苯甲酸和对羟基汞苯磺酸能够与蛋白质分子的半胱氨酸和组氨酸残基都发生反应。
