Endo-H在毕赤酵母中的表达、纯化及其在N-糖基化分析中的应用

Expression of endo-beta-N-acetylglucosaminidase H in Pichia pastoris and its application to N-glycosylation analysis

目的通过巴斯德毕赤酵母(Pichia pastoris)表达制备内切β-N-乙酰氨基葡糖苷酶-H(endo-beta-N-acetylglucosaminidase H,Endo-H),并用于蛋白质的N-糖基化分析。方法根据GenBank中公布的褶皱链霉菌(Streptomyces plicatus)Endo-H的cDNA序列,设计并合成Endo-H全基因,将其克隆至P.pastoris表达载体pPIC9中,重组质粒转化P.pastoris JC308宿主菌,工程菌经甲醇诱导,分泌表达Endo-H,目的蛋白经疏水层析、凝胶过滤两步纯化后,纯度可>95%。成品用于基于DNA测序的荧光辅助糖电泳(DNA sequencer assisted fluorophore-assisted carbohydrate electrophoresis,DSA-FACE)分析核糖核酸酶B(ribonuclease B,RNaseB)的糖基结构,比较了Endo-H与商品化N-糖酰胺酶F(peptide-N-asparigine amidase F,PNGase F)的糖基切割功能。结果利用P.pastoris表达制备EndoH,可切割天然或变性状态下的β-1,4-糖苷键连接的甘露糖型结构糖链,不能切割复杂型糖链糖蛋白;经DSAFACE分析,结果显示Endo-H酶切RNaseB后其糖链为Man5GlcNAc-Man9GlcNAc,PNGaseF酶切RNaseB的糖链为Man5GlcNAc2-Man9GlcNAc2,两者相差一个GlcNAc。结论通过P.pastoris制备的Endo-H具有天然生物活性,可用于蛋白质的N-糖基化结构分析。

Objective To prepare endo-beta-N-acetylglucosaminidase H （Endo-H） expressed in Pichia pastoris, and apply it to N-glycosylation analysis .Methods One complete gene was synthesized on the basis of the cDNA sequence encoding Streptomyces plicatus reported in GenBank .The gene was cloned into the expression vector pPIC 9.The expression vector pPIC9-Endo-H was transformed into P.pastoris（JC308）.The expression products were induced by methanol , puri-fied by two-step chromatography , used to analyze the glycan structures of RNaseB by the DNA sequencer assisted fluoro-phore-assisted carbohydrate electrophoresis （DSA-FACE）methods, and finally compared with peptide-N-asparagine amidase F（PNGase F）.Results This enzyme expressed in P.pastoris（JC308） had the ability to hydrolyze natural or denatured high-mannose type of oligosaccharide linked by β-1,4-glycosidic bonds , but not complex-type oligosaccharide .The result of DSA-FACE showed that carbohydrate chains of Man 5 GlcNAc-Man9 GlcNAc could be obtained when RNaseB was hydrolyzed by Endo-H, and that Man5 GlcNAc2-Man9 GlcNAc2 chains became available when RNaseB was hydrolyzed by PNGase F . Conclusion Endo-H expressed in P.pastoris has bioactivity which can be used to analyze N-glycosylation with the method of DSA-FACE.