Characterization of a cold adapted and salt tolerant exo chitinase (ChiC) from Pseudoalteromonas sp. DL 6
We have previously reported a non processive endo type chitinase, ChiA, from a newly isolated marine psychrophilic bacterium, Pseudoalteromonas sp. DL 6. In this study, a processive exo type chitinase, ChiC, was cloned from the same bacterium and characterized in detail. ChiC could hydrolyze crystalline chitin into (GlcNAc)2 as the only observed product. It exhibited high catalytic activity even at low temperatures, e.g. close to 0 degC, or in the presence of 5 M NaCl, suggesting that ChiC was a cold adapted and highly salt tolerant chitinase. ChiC could also hydrolyze other substrates, including chitosan and Avicel, indicating its broad substrate specificity. Sequence features indicated that ChiC was a multi domain protein having a deep substrate binding groove that was regarded as characteristic of processive exo chitinases. Enzymatic hydrolysis of chitin by ChiC could be remarkably boosted in the presence of ChiA, suggesting the synergy of ChiC and ChiA. This work provided a new evidence to prove that marine psychrophilic bacteria utilized a synergistic enzyme system to degrade recalcitrant chitin.
Extremophiles