Internal Cleavage of Bacillus subtilis BSE616 Endo-$\beta$-1, 4-glucanase expressed in Escherichia coli

The cytoplasmic endo-$\beta$-l, 4-glucanase (endoglucanase) was purified from cell extracts of Escherichia coli (pBS1) transformant carrying the Bacillus subtilis endo-$\beta$-l, 4-glucanase gene after full growth, and its molecular weight was found to be 52 kilodaltons (kDa). The endo-$\beta$-l, 4-glucanase isolated from the periplasmic space was smaller than 52-kDa cytoplasmic enzyme. The 52-kDa endoglucanase was found to be cleaved in the periplasm and finally converted to 34.5-kDa protein. Small amounts of both 52-kDa and 34.5-kDa proteins were secreted into the culture broth. The cleavage took place in the C-terminal portion of the enzyme. The N-terminal amino acid residues of both 52-kDa and 34.5-kDa enzymes were determined to be the same, Ala, the 30th residue of the primary translation product. Cleavage of the C-terminal portion showed to have no significant effect on the basic enzyme properties.