Gargouri Y, Cudrey C, Mejdoub H, Verger R
Laboratoire de Biochimie, Ecole Nationale d'Ingénieurs de Sfax, Tunisia.
Eur J Biochem. 1992 Mar 15;204(3):1063-7. doi: 10.1111/j.1432-1033.1992.tb16729.x.
Both thiol groups of native human pancreatic lipase can react with the new hydrophobic sulfhydryl reagent 5-dodecyldithio-2-nitrobenzoic acid (Dod-S-NbS) in the absence of a denaturing agent. Here we describe for the first time the covalent and stoichiometric modification of the inaccessible SHII group of native pancreatic lipase, using a 16-fold molar excess of this hydrophobic sulfhydryl reagent. A direct correlation was found to exist between the covalent modification of this SHII group and the loss of lipase activity. The question has not yet been answered, however, as to how Dod-S-NbS reaches the SHII-containing residue, whereas classical hydrophilic sulfhydryl reagents are unable to do so. This difference in reactivity may be attributable to the hydrophobic character of Dod-S-NbS and its potential capacity to form aggregates inducing a conformational change in the lipase molecule.
在没有变性剂的情况下，天然人胰脂肪酶的两个巯基均可与新型疏水巯基试剂5-十二烷基二硫代-2-硝基苯甲酸（Dod-S-NbS）发生反应。在此，我们首次描述了使用16倍摩尔过量的这种疏水巯基试剂对天然胰脂肪酶中无法接近的SHII基团进行共价和化学计量修饰。发现该SHII基团的共价修饰与脂肪酶活性的丧失之间存在直接关联。然而，关于Dod-S-NbS如何到达含SHII的残基，而经典的亲水巯基试剂却无法做到这一点的问题，尚未得到解答。这种反应性的差异可能归因于Dod-S-NbS的疏水特性及其形成聚集体从而诱导脂肪酶分子构象变化的潜在能力。
