Hamre Anne Grethe, Lorentzen Silje Benedicte, Väljamäe Priit, Sørlie Morten
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, PO 5003, N-1432 Ås, Norway.
Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia.
FEBS Lett. 2014 Dec 20;588(24):4620-4. doi: 10.1016/j.febslet.2014.10.034. Epub 2014 Nov 5.
Glycoside hydrolases depolymerize polysaccharides. They can subtract single carbohydrate chains from polymer crystals and cleave glycosidic bonds without dissociating from the substrate after each catalytic event. This processivity is thought to conserve energy during polysaccharide degradation. Herein, we compare the processivity of components of the chitinolytic machinery of Serratia marcescens. The two processive chitinases ChiA and ChiB, the ChiB-W97A mutant, and the endochitinase ChiC were analyzed for the extent of degradation of three different chitin substrates. Moreover, enzyme processivity was assessed on the basis of the [(GlcNAc)2]/[GlcNAc] product ratio. The results show that the apparent processivity (Papp) greatly diminishes with the extent of degradation and confirm the hypothesis that Papp is limited by the length of obstacle free path on the substrate.
糖苷水解酶可使多糖解聚。它们能够从聚合物晶体中去除单个碳水化合物链，并在每次催化事件后不与底物解离的情况下裂解糖苷键。这种持续性被认为在多糖降解过程中可节省能量。在此，我们比较了粘质沙雷氏菌几丁质分解机制各组分的持续性。分析了两种持续性几丁质酶ChiA和ChiB、ChiB-W97A突变体以及内切几丁质酶ChiC对三种不同几丁质底物的降解程度。此外，基于[(GlcNAc)2]/[GlcNAc]产物比率评估了酶的持续性。结果表明，表观持续性（Papp）随降解程度大幅降低，并证实了Papp受底物上无障碍路径长度限制这一假设。
