Chitinase-E from Chitiniphilus shinanonensis generates chitobiose from chitin flakes

Abstract

Enzymatic deconstruction of chitin to chitobiose is of significant interest in view of its various biological applications. Here we report detailed insights into the chitin degradation by chitinase-E from a chitinolytic bacterium Chitiniphilus shinanonensis (CsChiE). CsChiE was optimally active at 50 °C in 50 mM sodium phosphate pH-7.0. It showed a kcat and overall catalytic efficiency (Kcat/Km) as 3.9 × 103 s−1 and 0.6 × 103 s−1 mg−1 mL, respectively, on colloidal chitin (CC). CsChiE efficiently hydrolyzed crystalline polymers like α-, β- and CC and released chitobiose as the predominant product (11.3 mM on CC). Further, CsChiE displayed substantial activity towards the unmilled crab shell chitin waste (chitin-flakes) and generated chitobiose. Activity studies on chitooligosaccharides revealed that CsChiE produced chitobiose as the major product. Our results indicate that the multi-modular CsChiE is a non-processive exo-chitinase which is more suitable to generate chitobiose from a variety of chitinous substrates including unprocessed chitin-flakes.