Characterization of cold-active β-N-acetylglucosaminidase from Arctic bacterium Pseudoalteromonas issachenkonii KOPRI 22718

Abstract

One hundred thirty-six marine bacteria showing chitinolytic activity were isolated from 47 sediment samples of the Kara Sea, Arctic. Among them, a psychrotolerant strain (KOPRI 22718) was selected for its high exo-acting chitinase activity. The 16S rRNA sequence identifies KOPRI 22718 as Pseudoalteromonas issachenkonii. An exo-acting chitinase was homogeneously purified from the culture supernatant of KOPRI 22718 through ion exchange and gel filtration chromatography, and the molecular weight of purified chitinase was estimated to be approximately 112 kDa. Due to its β-N-acetylglucosaminidase activity, W-Chi22718 was able to produce N-acetyl-D-glucosamine monomers from chitin oligosaccharide substrates. W-Chi22718 displayed chitinase activity from 0-37°C (optimal temperature of 30°C), and maintained activity from pH 6.0-9.0 (optimal pH of 7.6). Interestingly, W-Chi22718 exhibited a relative activity of 13 and 35% of maximal activity at 0 and 10°C, respectively, which is comparable to the activities of previously characterized, cold-adapted, bacterial chitinases. W-Chi22718 activity was enhanced by K+, Ca2+, and Fe2+, but completely inhibited by Cu2+and SDS. We found that W-Chi22718 can produce much more N-acetyl-D-glucosamines from colloidal chitin, working together with, previously characterized, cold-active endochitinase W-Chi21702.