Production of hydrolytic enzymes by oral isolates of Eikenella corrodens

Abstract Thermus thermophilus cells harboring an expression plasmid for the aqualysin I gene secrete the mature enzyme into the medium. In an Escherichia coli expression system, a precursor of the enzyme with the C-terminal pro-sequence is accumulated in the cells, and upon treatment at 65°C the active enzyme is produced. One- to 10-amino acid residue deletions, as well as complete 105-residue deletion of the C-terminal pro-sequence from the C-terminus, did not affect the production of the enzyme in T. coli cells. T. thermophilus cells harboring plasmids for mutant precursors with one- and three-residue deletions secreted the enzyme extracellularly. However, transformants harboring plasmids for mutant precursors with deletions of five or more amino acid residues could not be obtained. These results suggest that the C-terminal pro-sequence plays an important role in the extracellular secretion of the enzyme in T. thermophilus cells.