Comparison of multicopy pro-microbial transglutaminase encoded gene expression in Pichia pastoris

Abstract

Transglutaminases catalyse the formation of an isopeptide bond between the group of γ-carboxamides of glutamine residues and primary amine groups of proteins. It is widely used in different food industries in dairy, meat, and bakery products. In this work, the effect of the copy number of gene expression cassette on the extracellular production of pro-MTGase under the GAP promoter in Pichia pastoris was elucidated. Expression vector carrying the Streptomyces mobaraensis pro-MTGase encoded gene was constructed and transformed into the P. pastoris X33. The production of pro-MTGase in single copy and three copies expression cassettes containing clones were compared under the same fermentation conditions. More than 30% enzyme activity was obtained from single copy expression cassette containing clone compared to three copies expression cassettes containing clone. Besides, the amount of the enzyme produced per cell was found to be 24% higher in the fermentation broth of single copy expression cassette containing clone. As a conclusion, there is an inverse correlation between the extracellular production of pro-MTGase and the copy number of gene expression cassette.