文献类型： 外文期刊

作者： Chen, L. L. ¹ ; Han, D. L. ¹ ; Zhai, Y. F. ¹ ; Wang, J. H. ² ; Wang, Y. F. ² ; Chen, M. ¹ ;

作者机构： 1.Shandong Univ, Sch Life Sci, State Key Lab Microbial Technol, Jinan 250100, Shandong, Peoples R China

2.Minist Agr, Key Lab Novel Food Resources Proc, Key Lab Agroprod Proc Technol Shandong Prov, Inst Agrofood Sci & Technol,Shandong Acad Agr Sci, Jinan 250100, Shandong, Peoples R China

关键词： UDP-galactose 4-epimerase (GalE);Streptococcus pneumoniae TIGR4;mutation;substrate specificity

期刊名称：BIOCHEMISTRY-MOSCOW （ 影响因子：2.487； 五年影响因子：2.57 ）

ISSN： 0006-2979

年卷期： 2018 年 83 卷 1 期

页码：

收录情况： SCI

摘要： Current clinical treatments for pneumococcal infections have many limitations and are faced with many challenges. New capsular polysaccharide structures must be explored to cope with diseases caused by different serotypes of Streptococcus pneumoniae. UDP-galactose 4-epimerase (GalE) is an essential enzyme involved in polysaccharide synthesis. It is an important virulence factor in many bacterial pathogens. In this study, we found that two genes (galE(sp1) and galE(sp2)) are responsible for galactose metabolism in pathogenic S. pneumoniae TIGR4. Both GalE(Sp1) and GalE(Sp2) were shown to catalyze the epimerization of UDP-glucose (UDP-Glc)/UDP-galactose (UDP-Gal), but only GalESp2 was shown to catalyze the epimerization of UDP-N-acetylglucosamine (UDP-GlcNAc)/UDP-N-acetylgalactosamine (UDP-GalNAc). Interestingly, GalE(Sp2) had 3-fold higher epimerase activity toward UDP-Glc/UDP-Gal than GalE(Sp1). The biochemical properties of GalE(Sp2) were studied. GalE(Sp2) was stable over a wide range of temperatures, between 30 and 70 degrees C, at pH 8.0. The K86G substitution caused GalE(Sp2) to lose its epimerase activity toward UDP-Glc and UDP-Gal; however, substitution C300Y in GalE(Sp2) resulted in only decreased activity toward UDP-GlcNAc and UDP-GalNAc. These results indicate that the Lys86 residue plays a critical role in the activity and substrate specificity of GalE(Sp2).