Abstract To clone and prokaryotic express the gene encoding Inosine 5-monophosphate dehydrogenase (impdh) of the Streptococcus suis serotype 2, and to investigate the immune antigenicity and enzymatic activity of gene product．The encoding impdh gene of 05ZYH33 strain isolated from patients in Ziyang county of Sichuan Province was amplified by PCR with the designed primers, and then cloned into prokaryotic expression plasmid pET28a, and the recombinant plasmid pET28a-impdh was transformed into E.coli BL21(DE3). After induced expression by IPTG, the fusion protein was purified by chromatography. The isolated IMPDH protein was analyzed with SDS-PAGE and Western blotting, and its enzymatic activity was measured at different pH and temperatures. High expression of IMPDH was obtained and the strongest enzymatic activity displayed at the optimal temperature and pH condition. The experimental results showed that the impdh gene 05ZYH33 can be highly expressed in prokaryotic system, and the recombinant protein showed specific antigenicity and had best enzymatic activity in optimal pH and temperature．
