BIOSYNTHESIS OF GLYCOPROTEINS IN Sporothrix schenckii: PURIFICATION AND BIOCHEMICAL CHARACTERIZATION OF AN ENDOPLASMIC RETICULUM α1,2‐ MANNOSIDASE

• Published in: The FASEB journal 2006-03, Vol.20 (5), p.A1364-A1364
• Main Authors: Robledo‐Ortiz, Claudia Iris, Mora‐Montes, Hector M, Gonzalez‐Sanchez, Laura C, Razo‐Ventura, Angel, Lopez‐Romero, Everardo
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.20.5.A1364

α‐Mannosidases are involved in the N‐glycans biosynthesis and degradation. An endoplasmic reticulum (ER) α1,2‐mannosidase that participates in N‐oligosaccharide processing by eliminating one mannose residue has been identified in Saccharomyces cerevisiae and Candida albicans. In Penicillium citrinum and Aspergillus nidulans, three Golgi α1,2‐mannosidases that eliminates four mannose residues from M9 have been identified. Actually, nothing is known about N‐glycan assembly in S. schenckii, a human pathogenic fungus. We partially purified both the membrane‐bound (MB) and soluble α‐mannosidase activities. By adding pepstatin A to the cell‐rupture buffer, the soluble activity was not detected, which suggest that most of the activity is MB. This α‐mannosidase was solubilized by a non conventional method. It exhibited a MW of 75 kDa, was recognized by anti‐α1,2‐mannosidase antibodies from C. albicans and had the ability to convert the substrate Man9GlcNAc2 into Man8GlcNAc2 isomer B. The fractionation of a protoplast homogenate showed that the enzyme is in the ER. These results and some biochemical data strongly suggest that the mechanism of N‐glycan processing by α1,2‐mannosidase from S. schenckii is similar to that previously reported for S. cerevisiae and C. albicans and it is a new member of the glycosyl hydrolases family 47. This work was partially supported by CONACyT and Universidad de Guanajuato.