中文摘要：

以高粱品系早亨加利为材料,通过RT–PCR扩增,克隆高粱Sb CAD4基因。测序结果表明,克隆的Sb CAD4基因与NCBI基因库中高粱IS11861品系只在编码序列第548位有1个碱基的差异,而二者的氨基酸序列完全一致。进化树分析结果表明,Sb CAD4与拟南介、水稻、玉米的木质素合成CAD基因位于同/L1个群中。比对分析结果表明,Sb CAD4与木质素合成基因具有相同的结构域。将构建正确的重组质粒（p MAL–Sb CAD4）转化入大肠杆菌菌种BL21中进行诱导表达的结果表明,IPTG的最佳诱导浓度为0.5 mmol/L。经Amylose Resin亲和层析柱纯化后,Sb CAD4融合蛋白在SDS–PAGE电泳分析时呈现1条蛋白带。利用纯化的蛋白对Sb CAD4进行酶活测定,其酶动力学参数Km值为5.2μmol/L,Vmax为5.8μmol/（min·mg）,表明Sb CAD4具有肉桂醇脱氢酶活性。

英文摘要：

Cinnamyl alcohol dehydrogenase （CAD）, which catalyzes the last step of monolignol biosynthesis, is a key enzyme in the biosynthesis of lignin. In this research, the gene SbCAD4 from Sorghum line Early Hegari-sart was amplified by RT-PCR and cloned into pMD18-T. There was only one base difference between the nucleotide sequence of the cloned gene and the SbCAD4 reference gene of Sorghum line IS 11861. But the amino acid sequence of cloned gene was consistent with IS 11861. Further phylogenetic analysis revealed that gene SbCAD4 belonged to the first group, which contained bona fide CAD genes from Arabidopsis, rice and maize. And it was also identified that SbCAD4 possessed the same motifs with these bona fide CAD genes through the alignment analysis. By verified a constructed recombinant plasmid （pMAL-SbCAD4） and transplanted it into Escherichia coli BL21, we found that the best expression concentration for SbCAD4-fused protein induction with IPTG was 0.5 mmol/L. The electrophoretic analysis showed that there was a single band in the SDS-PAGE gel after purified with affinity chromatography. The catalytic activity of purified protein was at the Km value Kmof 5.2 μmol/L and Vmax, value of 5.8 μmol/（min.mg）.