Gu Yayun, Lu Meiling, Wang Zongqiang, Wu Xuri, Chen Yijun
State Key Laboratory of Natural Medicines and Laboratory of Chemical Biology, China Pharmaceutical University, 24 Tongjia St., Nanjing, Jiangsu Province, 210009, P. R. China.
Chemistry. 2017 Feb 21;23(11):2548-2551. doi: 10.1002/chem.201605929. Epub 2017 Jan 27.
Glycosaminoglycans (GAG) lyases are useful biocatalysts for the preparation of oligosaccharides, but their substrate spectra are limited to the same family. Thus, the degradation activity across families of GAG lyases is advantageous and desirable for various applications. In this study, residue Lys130 at the substrate entrance of monomeric heparinase III from Pedobacter heparinus ATCC 13125 was replaced by cysteine, and the resulting mutant K130C showed novel catalytic activity in degrading hyaluronic acid without affecting its native activity toward heparin and heparan sulfate. The broadened catalytic promiscuity by mutant K130C was the result of dimerization through a disulfide bond to expand the substrate binding pocket. This bifunctional enzyme is potentially valuable in the degradation of different types of GAGs.
糖胺聚糖（GAG）裂解酶是制备寡糖的有用生物催化剂，但其底物谱仅限于同一家族。因此，GAG裂解酶跨家族的降解活性对于各种应用而言是有利且令人期待的。在本研究中，来自嗜肝素土杆菌ATCC 13125的单体肝素酶III底物入口处的第130位赖氨酸残基被半胱氨酸取代，所得突变体K130C在降解透明质酸时表现出新型催化活性，且不影响其对肝素和硫酸乙酰肝素的天然活性。突变体K130C催化选择性的拓宽是通过二硫键二聚化以扩大底物结合口袋的结果。这种双功能酶在降解不同类型的GAG方面具有潜在价值。
