In Silico Characterization of a Unique Plant-Like "Loopful" GH19 Chitinase from Newly Isolated Chitinophaga sp. YS-16

Abstract

Chitinases are glycohydrolases that cleave β-1,4 linkages in chitin and are grouped into glycohydrolase (GH) family 18 and 19. GH18 chitinases are found ubiquitously, whereas GH19 chitinases are confined predominantly to higher plants and few bacteria. In this study, a new chitinolytic bacterium, Chitinophaga sp. YS-16, was isolated and identified as a close relative of Chitinophaga pinensis DSM 2588 with 99.41% similarity of 16S rRNA sequence. The gene encoding for GH19 chitinase bearing unique domain architecture was amplified from the genomic DNA of YS-16. The sequence of GH19 chitinase (CpChi) encoded in the genome of YS-16 showed 90.5% identity with the sequence of GH19 chitinase encoded in genome of C. pinensis DSM 2588 (ACU62980.1). Bioinformatics analyses of CpChi revealed it to be a 'loopful' chitinase which has been reported only from plants till date. The tertiary structure of the catalytic domain of CpChi (CtCpChi) was predicted by homology modelling. The docking of modelled structure of CtCpChi with oligomers of N-acetyl-D-glucosamine (GlcNAc) revealed that the binding cleft of CtCpChi could accommodate an octamer of GlcNAc, not known in any other reported bacterial chitinase. Phylogenetic analysis supports CtCpChi to be plant-like GH19 chitinase.