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The dasD gene is located just downstream of the dasABC gene cluster, encoding components of an ABC transporter for uptake of a chitin-degradation product N,N'-diacetylchitobiose [(GlcNAc)(2) ] in Streptomyces coelicolor A3(2). To clarify the roles of the DasD protein in the degradation and assimilation of chitin, we obtained and characterized a recombinant DasD protein and a dasD-null mutant of S. coelicolor A3(2). The recombinant DasD protein produced in Escherichia coli showed N-acetyl-β-d-glucosaminidase (GlcNAcase) activity and its optimum temperature and pH were 40 °C and 7, respectively. dasD transcription was strongly induced in the presence of chitin, weakly by chitosan, but not by cellulose or xylan in S. coelicolor A3(2). Immuno-blot analysis demonstrated that DasD is a cytoplasmic protein. The dasD-null mutant exhibited cellular GlcNAcase activity which was comparable with that of the parent strain M145. DasD, thus, did not seem to be a major GlcNAcase. Induced extracellular chitinase activity in the dasD-null mutant was, interestingly, higher than M145, in the presence of colloidal chitin or (GlcNAc)(2) . In contrast to M145, (GlcNAc)(2) temporally accumulated in the culture supernatant of the dasD-null mutant in the presence of colloidal chitin., (© 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.)

The dasD gene is located just downstream of the dasABC gene cluster, encoding components of an ABC transporter for uptake of a chitin-degradation product N,N′-diacetylchitobiose [(GlcNAc)2] in Streptomyces coelicolor A3(2). To clarify the roles of the DasD protein in the degradation and assimilation of chitin, we obtained and characterized a recombinant Das D protein and a dasD-null mutant of S. coelicolor A3(2). The recombinant Das D protein produced in Escherichia coli showed N-acetyl-β- d-glucosaminidase ( Glc NAcase) activity and its optimum temperature and pH were 40 °C and 7, respectively. dasD transcription was strongly induced in the presence of chitin, weakly by chitosan, but not by cellulose or xylan in S. coelicolor A3(2). Immuno-blot analysis demonstrated that Das D is a cytoplasmic protein. The dasD-null mutant exhibited cellular Glc NAcase activity which was comparable with that of the parent strain M145. Das D, thus, did not seem to be a major Glc NAcase. Induced extracellular chitinase activity in the dasD-null mutant was, interestingly, higher than M145, in the presence of colloidal chitin or ( Glc NAc)2. In contrast to M145, ( Glc NAc)2 temporally accumulated in the culture supernatant of the dasD-null mutant in the presence of colloidal chitin. [ABSTRACT FROM AUTHOR]