title: Conversion of alpha1,2-mannosidase E-I from Candida albicans to alpha1,2-mannosidase E-II by limited proteolysis.
abstract: Previous studies demonstrated the presence in Candida albicans ATCC 26555 of two soluble alpha1,2-mannosidases: E-I and E-II. In contrast, in the C. albicans CAI-4 mutant only E-I was detected and it could be processed by a membrane-bound proteolytic activity from the ATCC 26555 strain, generating an active 43 kDa polypeptide. Here, alpha1,2-mannosidase E-I from strain ATCC 26555 was purified by conventional methods of protein isolation and affinity chromatography in Concanavalin A-Sepharose 4B. Analytical electrophoresis of the purified enzyme revealed two polypeptides of 52 and 23 kDa, the former being responsible for enzyme activity as revealed by zymogram analysis. Time course proteolysis with an aspartyl protease from Aspergillus saitoi, converted alpha1,2-mannosidase E-I into an active polypeptide of 43 kDa which trimmed Man(9)GlcNAc(2), generating Man(8)GlcNAc(2) isomer B and mannose. Trimming was inhibited preferentially by 1-deoxymannojirimycin. Both, the molecular mass and the enzyme properties of the proteolytic product were identical to those described for alpha1,2-mannosidase E-II therefore supporting the notion that E-I is the precursor of E-II.
authors.affiliation: Instituto de Investigación en Biología Experimental, Facultad de Química, Universidad de Guanajuato, Apartado postal 187, Guanajuato, Gto, CP 36000, Mexico.
authors.forename: Héctor Manuel
authors.initials: HM
authors.lastname: Mora-Montes
authors.forename: Everardo
authors.initials: E
authors.lastname: López-Romero
authors.forename: Samuel
authors.initials: S
authors.lastname: Zinker
authors.forename: Patricia
authors.initials: P
authors.lastname: Ponce-Noyola
authors.forename: Arturo
authors.initials: A
authors.lastname: Flores-Carreón
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D002176:Candida albicans / Q000378:metabolism*; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D008361:Mannosidases / Q000378:metabolism*; D009844:Oligosaccharides / Q000737:chemistry / Q000378:metabolism
chemical_list: D009844:Oligosaccharides; D008361:Mannosidases; C046090:mannosyl-oligosaccharide 1,2-alpha-mannosidase; D016282:Aspartic Acid Endopeptidases