Springman E B, Angleton E L, Birkedal-Hansen H, Van Wart H E
Department of Chemistry, Florida State University, Tallahassee 32306.
Proc Natl Acad Sci U S A. 1990 Jan;87(1):364-8. doi: 10.1073/pnas.87.1.364.
Latent human fibroblast collagenase (HFC) can be activated by a variety of seemingly disparate means. In addition to the well-characterized activation by trypsin and organomercurial compounds, the enzyme can be activated to various extents by surfactants such as sodium dodecyl sulfate, by chaotropic ions such as SCN-, by disulfide compounds such as oxidized glutathione, by sulfhydryl alkylating agents such as N-ethylmaleimide, and by oxidants such as NaOCl. The underlying basis for these activations is the modification, exposure, or proteolytic release of the Cys73 residue from its habitat in the latent enzyme where it is thought to be complexed to the active-site zinc atom. This residue is not accessible for reaction with small molar excesses of dithionitrobenzoate in native, latent HFC. However, on addition of EDTA, this residue becomes fully exposed and is quantitatively labeled. All modes of activation of latent HFC are believed to involve the dissociation of Cys73 from the active-site zinc atom and its replacement by water, with the concomitant exposure of the active site. This is thought to be the primary event that precedes the well-known autolytic cleavages that are observed following the appearance of collagenase activity. The dissociation of Cys73 from the zinc atom in the latent enzyme "switches" the role of the zinc from a noncatalytic to a catalytic one. This "cysteine switch" mechanism of regulation may be applicable to the entire collagenase gene family.
潜在的人成纤维细胞胶原酶（HFC）可通过多种看似不同的方式被激活。除了已被充分表征的胰蛋白酶和有机汞化合物激活外，该酶还可被诸如十二烷基硫酸钠之类的表面活性剂、诸如SCN⁻之类的离液序列高的离子、诸如氧化型谷胱甘肽之类的二硫化合物、诸如N - 乙基马来酰亚胺之类的巯基烷基化剂以及诸如NaOCl之类的氧化剂在不同程度上激活。这些激活作用的潜在基础是Cys73残基从其在潜在酶中的所处位置发生修饰、暴露或蛋白水解释放，在潜在酶中它被认为与活性位点的锌原子形成复合物。在天然的潜在HFC中，该残基无法与小摩尔过量的二硫代硝基苯甲酸发生反应。然而，加入EDTA后，该残基会完全暴露并被定量标记。潜在HFC的所有激活模式都被认为涉及Cys73从活性位点锌原子上解离并被水取代，同时活性位点暴露。这被认为是在胶原酶活性出现后观察到的众所周知的自溶裂解之前的主要事件。潜在酶中Cys73从锌原子上解离会使锌的作用从非催化转变为催化。这种“半胱氨酸开关”调控机制可能适用于整个胶原酶基因家族。
