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The glycosylation patterns of phytase (E C 3.1.3.8) from Aspergillus niger NRRL 3135 with recombinant phytase from A. niger van Tieghem were compared. The following characteristics were studied: size of the whole molecule, type of linkage (N-linked or O-linked oligosaccharide), profile (number of different type of oligosaccharides present), monosaccharide composition, their order, and configuration. The molecular weights of both glycoproteins, after deglycosylation, was approximately 55 kDa as determined by SDS-PAGE. Both glycoproteins were about 35.29% glycosylated (calculations were made on the basis of 85 kDa molecular weight before deglycosylation). Only N-linked oligosaccharides were present. When N-linked oligosaccharides were released and labeled, the same profile was obtained for both glycoproteins. Mannose residues were detected after digestion by combinations of various exoglycosidases. N-acetylneuraminic acid, galactose, and N-acetylglucosamine residues were not detected. Released mannose residues were (alpha 1-2,3,6) linked. The trisaccharide core structure was nonfucosylated for all the oligosaccharides released from both glycoproteins. The only major difference found between the two glycoproteins was the migration pattern of oligosaccharide bands on gel after digestion with alpha-mannosidases. The structure of N-linked oligosaccharides ranged from (Man)5(GlcNAc)2 to (Man)10 (GlcNAc)2.

The crude extracellular extract of Aspergillus niger (syn A. ficuum) NRRL 3135 contains glucoamylase (exo-1,4-alpha-D-glucanohydrolase, EC 3.2.1.2). The enzyme, a glycoprotein, was purified 7-fold by ion-exchange chromatography, chromatofocusing, and conconavalin A affinity chromatography. The molecular weight of the enzyme was estimated to be 90 kDa by SDS-PAGE and gel permeation chromatography. The pI of the enzyme was 3.4. The temperature optimum of the enzyme was 60 degrees C and the pH optimum was 5.0. The Vmax values for soluble starch, maltose, maltotriose, maltotretraose, maltopentaose, and isomaltose were 55.2, 11.7, 32.3, 47.8, 59.2, 12.5 nKat glucose/sec, respectively and the Km values for the same substrates were 0.09%, 0.67 mM, 0.76 mM, 0.76 mM, 0.68 mM, and 122.01 mM, respectively.