Identification of chitinases Is-chiA and Is-chiB from Isoptericola jiangsuensis CLG and their characterization

A 274-bp conserved fragment of chiA (chiA-CF) was amplified from the genomic DNA of Isoptericola jiangsuensis CLG (DSM 21863, CCTCC AB208287) using the specific PCR primers. Based on chiA-CF sequences, a 5233-bp DNA fragment was obtained by self-formed adaptor PCR. DNA sequencing analysis revealed there were two contiguous open reading frames coding for the precursors of Is-chiA [871 amino acids (aa)] and Is-chiB (561 aa) in the 5233-bp DNA fragment. The Is-chiA and Is-chiB exhibited 58% and 62% identity with ArChiA and ArChiB chitinase from Arthrobacter sp. TAD20, respectively. The Is-chiA and Is-chiB genes were cloned into expression vector pET28a (+) and expressed in Escherichia coli BL21 (DE3) with isopropyl-β-D-thiogalactopyranoside induction. Is-chiA and Is-chiB were 92 kDa and 60 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and showed chitobiosidase and endochitinase activity, respectively. Is-chiA and Is-chiB were purified by Ni-nitrilotriacetic acid affinity chromatography and the characteristics of both Is-chiA and Is-chiB were studied.