Cloning of exo-β-1,3-glucanase gene from a marine yeast Williopsis saturnus and its overexpression in Yarrowia lipolytica.

The exo-β-1,3-glucanase structural gene (WsEXG1 gene, accession number: FJ875997.2) was isolated from both the genomic DNA and cDNA of the marine yeast Williopsis saturnus WC91-2 by inverse PCR and RT-PCR. An open reading frame of 1,254 bp encoding a 417 amino acid protein (isoelectric point: 4.5) with calculated molecular weight of 46.2 kDa was characterized. The promoter of the gene (intronless) was located from -28 to -77 and had one TATA box while its terminator contained the sequence AAGAACAATAAACAA from +1,386 to +1,401. The protein had the Family 5 glycoside hydrolase signature IGLELLNEPL and a fragment with the sequence of NLCGEWSAA, where the Glu-310 (E) was considered to be the catalytic nucleophile. The WsEXG1 gene was overexpressed in Yarrowia lipolytica Po1h and the recombinant WsEXG1 was purified and characterized. The molecular weight of the purified rWsEXG1 was 46.0 kDa. The optimal pH and temperature of the purified rWsEXG1 were 5.0°C and 40°C, respectively. The purified rWsEXG1 had high exo-β-1,3-glucanase activity. Therefore, the recombinant β-1,3-glucanase may have highly potential applications in food and pharmaceutical industries.