ChiA74 is a secreted endochitinase produced by Bacillus thuringiensis. Previously we have partially characterized the physical parameters that affect enzymatic activity of ChiA74 in crude preparations of bacterial secretomes. In the present study, we cloned the chiA74 open reading frame (ORF) lacking the 5' sequence coding for its secretion signal peptide (chiA74 Delta sp) into a cold shock expression vector (pColdI) for production of the enzyme in Escherichia coli BL21-Rosetta 2. As a result, the N-terminal end of ChiA74 Delta sp ORF was fused to an artificial sequence of 28 amino acid, including a 6x histidine tag for purification of recombinant 6xHis tagged-Chi Delta 74Asp (rChiA74, similar to 74 kDa). Along with a protein of similar to 74 kDa, we co-purified its similar to 55 kDa processed form which was confirmed by Western blot analysis. Optimal endochitinase activity of purified rChiA74 occurred at pH 7 and 40 degrees C. Most divalent cations (e.g. Ba+2, Ca+2, Mn+2, Zn+2 and Cu+2) at concentration of 10 mM reduced chitinase activity by similar to 30%, and Hg+2 (10 mM) drastically inhibited ChiA74 activity by similar to 75-100%. The V-max, K-m and k(cat) for rChiA74 were 0.11 +/- 0.01 nmol/min, 2.15 mu M +/- 0.45 and 3.81 s(-1), respectively, using 4-MU-GlcNAc(3) as substrate. Using purified rChiA74 and colloidal chitin as substrate, chitin-derived oligosaccharides with degree of polymerization of 2 and 1 were detected. (c) 2014 Elsevier Inc. All rights reserved.