[Cloning and expression of UDP-glucose-4-epimerase gene from Streptomyces and characteristics of the enzyme].
ABSTRACT The ste 19 gene is identified to encode a UDP-Glucose-4-epimerase by data base comparison and experimental validation. The enzyme catalyzes the interconversion of UDP-Glucose and UDP-Galactose. The gene amplified by PCR with the total DNA of Streptomyces sp. 139 as template was cloned into plasmid pET30a at Xho I - Nde I sites. After the recombinant plasmid was transformed into E. coli BL21 (DE3) and induced by IPTG, the protein was expressed as high as 26% of the total cell proteins and dominantly as soluble protein form. The high GC content (73.8%) and the preferential usage of G or C as third base of codons (96.2%) seems not to affect its good expression in E. coli BL21 (DE3). The purity of the recombinant protein purified by Ni2+ affinity chromatography is 92.9% by HPLC analysis. Enzyme activity assay shows the recombinant protein is a UDP-Glucose-4-epimerase and its activity is not dependent on exogenous NAD+. The above research lays a very good foundation for study on functions of the ste 19 gene in Ebosin biosynthesis.