Properties of a beta-D-mannosidase from Aspergillus niger.
The beta-D-mannosidase (beta-D-mannoside mannohydrolase, EC 3.2.1.25) from culture filtrate of Aspergillus niger has been purified in large amounts by fractionation with (NH4)2SO4 and DEAE-cellulose chromatography. The removal of traces of alpha-D-galactosidase was performed on a Sepharose-epsilon-aminocaproyl-galactosylamine column. The final enzyme preparation (specific activity 188 units) has no other glycosidase activity and is judged homogeneous. The enzyme has a molecular weight of 130 000 +/- 5000 and an isoelectric point of 4.7. The amino acid composition of the enzyme is characterized by high proportion of acidic amino acids and no cysteine residues and a single chain structure of the enzyme is suggested. The enzyme shows maximum activity on p-nitrophenyl-beta-D-mannopyrano-side at pH 3.5 and at 55 degrees C. The presence of 80% of beta-sheet structure in the protein and 20.8% of monosaccharides (Gal : 1.3; Man : 7; GlcNAc : 1) could explain this relative high heat stability (up to 2 h at 55 degrees C). Enzyme activity is inhibited by mannose (Ki = 7.85 mM) and the specificity is examined.
D000596:Amino Acids / Q000032:analysis; D001234:Aspergillus niger / Q000201:enzymology*; D002413:Cations, Divalent / Q000494:pharmacology; D007700:Kinetics; D008358:Mannose / Q000494:pharmacology; D008361:Mannosidases / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D013379:Substrate Specificity; D013696:Temperature
D000596:Amino Acids; D002413:Cations, Divalent; D008361:Mannosidases; D008358:Mannose