Tunicamycin inhibition of N-glycosylation of α-glucosidase from Aspergillus niveus: partial influence on biochemical properties

Isolation and characterization of an aspartic protease able to hydrolyze and decolorize heme proteins from Aspergillus glaucus

BACKGROUND

The xerophilic Aspergillus molds, Aspergillus glaucus and Aspergillus repens, have been used in the ripening and fermentation of dried tuna bonito (katsuobushi). These molds, and especially their extracellular hydrolytic enzymes, may also be of wider industrial value.

RESULTS

Aspergillus glaucus strain MA0196 produces different types of hydrolytic enzymes, including amylase, serine protease, aspartic protease, lipase and cellulase, depending on the composition of the medium. We characterized several of these enzymes, focusing on a glycosylated aspartic protease. The results showed that the lower the d-glucose concentration in the medium, the higher the degree of protease glycosylation, with excess glycosylation tending to decrease protease activity. The molecular mass of the glycosylated protease as determined by gel filtration and sodium dodecyl sulphate-polyacrylamide gel electrophoresis was 243 and 253 kDa, respectively. The chemically deglycosylated protease had a molecular mass of only 46 kDa. The amount of myoglobin-decolorizing activity was similar to that of a previously reported aspartic protease from A. repens strain MK82. However, the strain MA0196 protease more broadly hydrolyzed myoglobin and hemoglobins than did the strain MK82 protease.

CONCLUSION

The results of the present study demonstrate the potential utility of Aspergillus molds as a functionally new microbial resource for industrial applications such as the bleaching of heme proteins. © 2018 Society of Chemical Industry.

Influence of N-glycans on Expression of Cell Wall Remodeling Related Genes in Paracoccidioides brasiliensis Yeast Cells

Paracoccidioidomycosis is the most prevalent systemic mycosis in Latin America. It is caused by the temperature-dependent dimorphic fungus Paracoccidioides brasiliensis. The P. brasiliensis cell wall is a dynamic outer structure, composed of a network of glycoproteins and polysaccharides, such as chitin, glucan and N-glycosylated proteins. These glycoproteins can interact with the host to affect infection rates, and are known to perform other functions. We inhibited N-linked glycosylation using tunicamycin (TM), and then evaluated the expression of P. brasiliensis genes related to cell wall remodeling. Our results suggest that cell wall synthesis related genes, such as β-1,3-glucanosyltransferase (PbGEL3), 1,3-β-D-glucan synthase (PbFKS1), and α-1,4-amylase (PbAMY), as well as cell wall degrading related genes, such as N-acetyl-β-D-glucosaminidase (PbNAG1), α-1,3-glucanase (PbAGN), and β-1,3-glucanase (PbBGN1 and PbBGN2), have their expression increased by the N-glycosylation inhibition, as detected by qRT-PCR. The observed increases in gene expression levels reveal possible compensatory mechanisms for diminished enzyme activity due to the lack of glycosylation caused by TM.