Influences of N-linked glycosylation on the biochemical properties of aspartic protease from Aspergillus glaucus MA0196

Abstract

Abstract Aspergillus glaucus MA0196 produces a highly glycosylated aspartic protease (PepA_MA0196) that shows hydrolytic and decolorization activities toward hemoglobin. Sequence analysis of PepA_MA0196 indicated two potential N-glycosylation consensus sites, at Asn131 and Asn275. To elucidate the role of N-glycosylation in the biochemical properties of PepA_MA0196 and the resulting effects, recombinant PepA_MA0196 and three mutant proteases deglycosylated via site-direct mutagenesis were heterologously expressed in Pichia pastoris. After hydrolysis of the enzymes by PNGase F or Endo H, the molecular masses on SDS-PAGE of the enzymatically deglycosylated wild-type PepA_MA0196 and recombinant and single-mutant proteases were identical to that of the double-mutant protease (42.2 kDa). PepA_MA0196 and its recombinant were stable over a broader pH range and more thermostable than the deglycosylated mutant proteases, especially the double-mutant protease. In addition, PepA_MA0196 retained a higher activity at low water activity than did the double-mutant protease. The commercial applications of the glycosylated protease from strain MA0196 include hydrolysis of the heme proteins in dried tuna meat under low water content. Hemoprotein lysis is also a property of interest to the meat processing and detergent industries.