Softwood hemicellulose-degrading enzymes from Aspergillus niger: purification and properties of a beta-mannanase.
The enzymes needed for galactomannan hydrolysis, i.e., beta-mannanase, alpha-galactosidase and beta-mannosidase, were produced by the filamentous fungus Aspergillus niger. The beta-mannanase was purified to electrophoretic homogeneity in three steps using ammonium sulfate precipitation, anion-exchange chromatography and gel filtration. The purified enzyme had an isoelectric point of 3.7 and a molecular mass of 40 kDa. Ivory nut mannan was degraded mainly to mannobiose and mannotriose when incubated with the beta-mannanase. Analysis by 1H NMR spectroscopy during hydrolysis of mannopentaose showed that the enzyme acts by the retaining mechanism. The N-terminus of the purified A. niger beta-mannanase was sequenced by Edman degradation, and comparison with Aspergillus aculeatus beta-mannanase indicated high identity. The enzyme most probably lacks a cellulose binding domain since it was unable to adsorb on cellulose.
Ademark
P
P
Department of Biochemistry, Lund University, Sweden.
Varga
A
A
Medve
J
J
Harjunpää
V
V
Drakenberg
T
T
Tjerneld
F
F
Stålbrand
H
H
D000595:Amino Acid Sequence; D001234:Aspergillus niger / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D001673:Biodegradation, Environmental; D001709:Biotechnology; D006868:Hydrolysis; D007526:Isoelectric Point; D008351:Mannans; D008361:Mannosidases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008970:Molecular Weight; D011134:Polysaccharides / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014934:Wood; D044902:beta-Mannosidase
D008351:Mannans; D011134:Polysaccharides; C007916:hemicellulose; D008361:Mannosidases; D044902:beta-Mannosidase