Molecular cloning and sequence analysis of a PVGOX gene encoding glucose oxidase in Penicillium viticola F1 strain and it's expression quantitation

• The PVGOX gene from Penicillium viticola F1 was cloned by Genome Walking and their expression analysis was done by RT-PCR.
• An open reading frame of 1,806 bp encoding a 601 amino acid protein (isoelectric point: 5.01) was characterized.
• The protein deduced from the PVGOX gene had a signal peptide containing 17 amino acids.
• The Gox protein had three cysteine residues and six potential N-linked glycosylation sites.
• The relative transcription level of the PVGOX gene was also stimulated in the presence of calcium carbonate and CSL.
• Therefore, the GOX enzyme produced by P. viticola F1 might be good for the industrial level production of gluconic acid.

The PVGOX gene (accession number: KT452630) was isolated from genomic DNA of the marine fungi Penicillium viticola F1 by Genome Walking and their expression analysis was done by Fluorescent RT-PCR. An open reading frame of 1806 bp encoding a 601 amino acid protein (isoelectric point: 5.01) with a calculated molecular weight of 65,535.4 was characterized. The deduced protein showed 75%, 71%, 69% and 64% identity to those deduced from the glucose oxidase (GOX) genes from different fungal strains including; Talaromyces variabilis, Beauveria bassiana, Aspergillus terreus, and Aspergillus niger, respectively. The promoter of the gene (intronless) had two TATA boxes around the base pair number − 88 and − 94 and as well as a CAAT box at − 100. However, the terminator of the PVGOX gene does not contain any polyadenylation site (AATAAA). The protein deduced from the PVGOX gene had a signal peptide containing 17 amino acids, three cysteine residues and six potential N-linked glycosylation sites, among them, − N-K-T-Y- at 41 amino acid, − N-R-S-L- at 113 amino acid, − N-G-T-I- at 192 amino acid, − N-T-T-A at 215 amino acid, − N-F-T-E at 373 amino acid and –N-V-T-A- at 408 amino acid were the most possible N-glycosylation sites. Furthermore, the relative transcription level of the PVGOX gene was also stimulated in the presence of 4% (w/v) of calcium carbonate and 0.5 % (v/v) of CSL in the production medium compared with that of the PVGOX gene when the fungal strain F1 was grown in the absence of calcium carbonate and CSL in the production medium, suggesting that under the optimal conditions, the expression of the PVGOX gene responsible for gluconic acid biosynthesis was enhanced, leading to increased gluconic acid production. Therefore, the highly glycosylated oxidase enzyme produced by P. viticola F1 strain might be a good producer in the fermentation process for the industrial level production of gluconic acid.