Putative Role of a Streptomyces coelicolor-Derived alpha-Mannosidase in Deglycosylation and Antibiotic Production

Abstract

SCO0948 was found to be the single open reading frame annotated to encode an alpha-mannosidase (AM1) in Streptomyces coelicolor M145. To characterize the protein, we overexpressed SCO0948 in Escherichia coli BL21(DE3). Recombinant AM1, with a molecular weight of 110 kDa, exhibited alpha-mannosidase activity toward 4-nitrophenyl-alpha-D-mannopyranoside with a K-m of 4.61 mM, a V-max of 101.6 mM/min, and a specific activity of 47.96 U/mg. Treatment of ovalbumin, a glycoprotein, with AM1 resulted in partial deglycosylation, as assessed by glycostaining and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The S. coelicolor deletion mutant for SCO0948 failed to produce a-mannosidase activity, confirming AM1 as the only alpha-mannosidase in S. coelicolor M145. Interestingly, the deletion mutant and a complementation strain produced lower levels of the antibiotics actinorhodin and undecylprodigiosin in glucose minimal media. The results indicate that AM1 as an alpha-mannosidase influences deglycosylation and antibiotic production in S. coelicolor M145.