Kinetic properties of Streptococcus pneumoniae hyaluronate lyase
Kinetic properties of Streptococcus pneumoniae hyaluronate lyase
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DOI：
10.1093/glycob/11.4.297
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发表时间：
2001-04-01
期刊：
影响因子：
4.3
通讯作者：
Jedrzejas, MJ
中科院分区：
文献类型：
--
作者：
Kelly, SJ;Taylor, KB;Jedrzejas, MJ
肺炎链球菌透明质酸裂解酶是这种细菌性病原体的表面抗原，它在世界范围内引起大量的死亡率和发病率。这种酶的主要功能是降解透明质酸，这是几乎所有脊椎动物组织细胞外基质的主要成分。该酶使用一种过程作用模式将透明质酸降解为最终产物，即不饱和双糖透明质酸单位。这种催化通过五步质子接受和给予机制进行，包括底物结合、催化、释放双糖产物、剩余透明质酸底物的易位以及与微环境的质子交换。基于对天然酶及其与六糖底物和双糖产物配合物的三维结构分析，选择了几个残基进行突变研究，这些突变残基包括催化残基Asn349、His399、Tyr408，以及负责底物结合和易位的残基Arg243和Asn580。将野生型与突变型酶的动力学特性进行比较，可以对每个突变体进行表征，并将酶的动力学特性与其结构进行关联。野生型透明质酸裂解酶与其他多糖降解酶，水解酶核酸内切酶和葡萄糖淀粉酶的比较表明，所有这些不同的酶的K(m)s惊人的相似。
Streptococcus pneumoniae hyaluronate lyase is a surface antigen of this bacterial pathogen, which causes significant mortality and morbidity in human populations worldwide. The primary function of this enzyme is the degradation of hyaluronan, a major component of the extracellular matrix of the tissues of practically all vertebrates. The enzyme uses a processive mode of action to degrade hyaluronan to a final product, an unsaturated disaccharide hyaluronan unit. This catalysis proceeds via a five-step proton acceptance and donation mechanism that includes substrate binding, catalysis, release of the disaccharide product, translocation of the remaining hyaluronan substrate, and proton exchange with microenvironment.Based on the analysis of the three-dimensional structure of the native enzyme and its complexes with hexasaccharide substrate and disaccharide product, several residues have been chosen For mutation studies, These mutated residues included the catalytic residues Asn349, His399, Tyr408, and residues responsible for substrate binding and translocation, Arg243 and Asn580, The comparison of the kinetic properties of the wild-type with the mutant enzymes allowed for the characterization of every mutant and the correlation of the kinetic properties of the enzyme with its structure. The comparison of the wild-type hyaluronate lyase with other polysaccharide-degrading enzymes, the hydrolases endonuclease and glucoamylase, shows striking similarity of K(m)s for all of these different enzymes.