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A highly efficient β-1,4-glucosidase (BGL) secreting strain, Stereum hirsutum SKU512, was isolated and identified based on morphological features and sequence analysis of internal transcribed spacer rDNA. A BGL containing a carbohydrate moiety was purified to homogeneity from S. hirsutum culture supernatants using only a single chromatography step on a gel filtration column. The relative molecular weight of S. hirsutum BGL was determined as 98 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis or 780 kDa by size exclusion chromatography, indicating that the enzyme is an octamer. S. hirsutum BGL showed the highest activity toward p-nitrophenyl-β-D-glucopyranoside ( Vmax = 3,028 U mg-protein−1, kcat = 4,945 s−1) ever reported. The enzyme also showed good stability at an acidic pH ranging from 3.0 to 5.5. The BGL was able to promote transglycosylation with an activity of 42.9 U mg-protein−1 using methanol as an acceptor and glucose as a donor. The internal amino acid sequences of the isolated enzyme showed significant homology with hydrolases from glycoside hydrolase family 1 (GH1), indicating that the S. hirsutum BGL is a member of GH1 family. The characteristics of S. hirsutum BGL could prove to be of interest in several potential applications, especially in enhancing flavor release during the wine fermentation process. [ABSTRACT FROM AUTHOR]

Aspergillus niger K10 cultivated on 2-cyanopyridine produced high levels of an intracellular nitrilase, which was partially purified {18.6-fold) with a 24% yield. The N-terminal amino acid sequence of the enzyme was highly homologous with that of a putative nitrilase from Aspergillus fumigatus Af293. The enzyme was copurified with two proteins, the N-terminal amino acid sequences of which revealed high homology with those of hsp60 and an ubiquitin-conjugating enzyme. The nitrilase exhibited maximum activity (91.6 U mg"1) at 45°C and pH 8.O. Its preferred substrates, in the descending order, were 4-cyanopyridine, benzonitrile, 1,4-dicyanobenzene, thio- phen-2-acetonitrile, 3-chlorobenzonitrile, 3-cyanopyridine, and 4-chlorobenzonitrile. Formation of amides as byproducts was most intensive, in the descending order, for 2-cyanopyridine, 4-chlorobenzonitrile, 4-cyanopyridine, and 1,4-dicyanobenzene. The enzyme stability was markedly improved in the presence of D-sorbitol or xylitol (20% wfv each). p-Hydroxymercuribenzoate and heavy metal ions were the most powerful inhibitors of the enzyme. [ABSTRACT FROM AUTHOR]