CO-OVEREXPRESSION OF FOLDING MODULATORS IMPROVES THE SOLUBILITY OF THE RECOMBINANT GUINEA PIG LIVER TRANSGLUTAMINASE EXPRESSED IN ESCHERICHIA COLI

ABSTRACT Transglutaminases (EC 2.3.2.13) catalyze the formation of e-(γ-glutamyl)lysine cross-links and the substitution of primary amines for the γ-carboxamide groups of protein bound glutamine residues, and are involved in many biological phenomena. Transglutaminase reactions are also applicable in applied enzymology. Here, we established an expression system of recombinant mammalian tissue-type transglutaminase with high productivity. Overexpression of guinea pig liver transglutaminase in Escherichia coli, using a plasmid pET21-d, mostly resulted in the accumulation of insoluble and inactive enzyme protein. By the expression culture at lower temperatures (25 and 18°C), however, a fraction of the soluble and active enzyme protein slightly increased. Co-overexpression of a molecular chaperone system (DnaK-DnaJ-GrpE) and/or a folding catalyst (trigger factor) improved the solubility of the recombinant enzyme produced in E. coli cells. The specific activity, the affinity to the amine substrate, and the sen...