Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.21 (beta-glucosidase)
 3,280 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An extracellular xylanase was purified to homogeneity from the culture filtrate of a thermophilic fungus, Thermomyces lanuginosus-SSBP, and its biochemical characteristics were studied. A yield of 70-80% was achieved through the procedures of 80%-satd. ammonium sulphate precipitation, DEAE-Sephadex A25 and quaternary aminoethyl (QAE)-Sephadex A25 column chromatography. The molecular mass of the purified xylanase was 23.6 kDa, as analysed by SDS/PAGE, with a pI value of 3.8. The molar absorption coefficient of the absorbance at 280 nm was 6.8x10(4) M(-1).cm(-1). The specific activity, calculated using the dinitrosalicylic acid (DNS) method, was 3500 units/mg. The enzyme reactions followed Michaelis-Menten kinetics with K app m and V(max) values of 3.26 mg/ml and 6300 units/ml per mg of protein respectively, as obtained from a Lineweaver-Burk plot. The xylanase contained no other enzyme activity (cellulase, beta-glucosidase, beta-mannosidase, alpha-arabinofuranosidase, or beta-xylosidase) except for the hydrolysis of xylan substrate. The optimal temperature of the enzyme assay was 70-75 degrees C. The enzyme retained full activity after a 60 degrees C incubation for 3 h. The optimal pH of xylanase activity was 6.5 and the enzyme appeared to be stable over a broad pH range (pH 5-12) under the assay conditions. The majority of the metal ions tested had no effect on the enzyme activity, with the exception of Pb(2+) (modest inhibitor) and Hg(2+) (strong inhibitor). The results showed that one or two tryptophan residues oxidized by N-bromosuccinamide per enzyme molecule was sufficient to inhibit the enzyme activity completely, thus indicating that the tryptophan residues play an important role in the catalytical processes of the enzyme reaction. Because of the outstanding properties of the purified xylanase from the SSBP strain, this xylanase has a potential use in biopulping processes and other industrial applications.
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PMID:Purification and biochemical characteristics of beta-D-xylanase from a thermophilic fungus, Thermomyces lanuginosus-SSBP. 1046 22

The beta-D-glucosidase produced by Thermomyces lanuginosus-SSBP was purified to apparent homogeneity. The purified enzyme consisted of two identical subunits with a native molecular mass of 200 kDa. The purified beta-D-glucosidase only hydrolysed the glucoside substrates containing a terminal, non-reducing beta-D-glucose residue and was active on both aryl-beta-glucoside and cellobiose. This enzyme also exhibited less, but significant alpha-D-glucosidase activity and was capable of hydrolysing beta-1,6-linked diglucosides and gentiobiose. The Kapp m, V(max) and k(cat) values for p-nitrophenyl-beta-D-glucopyranoside were calculated to be 0.075 mM, 12.12 units/mg of protein and 44.44 glucose molecules released/s respectively. The beta-D-glucosidase retained its full activity after a 30 min incubation at 50 degrees C but was inactive after the same treatment at 70 degrees C. The enzyme appeared to be stable when the pH of the storage buffer was above 5.0. Maximal beta-D-glucosidase activity occurred at 65 degrees C and pH 6.0. This enzyme was competitively inhibited by glucose, cellobiose and salicin with K(i) values of 0.55, 0.52 and 0.81 mM respectively. The presence of Hg(2+) and N-bromosuccinimide inhibited the enzyme activity completely at 2 mM, while cysteine enhanced beta-D-glucosidase activity.
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PMID:Purification and biochemical characteristics of beta-D-glucosidase from a thermophilic fungus, Thermomyces lanuginosus-SSBP. 1046 23

Shake-flask cultivation of T. lanuginosus strain SSBP on coarse corn cobs yielded beta-xylanase levels of 56,500 nkat/ml at 50 degrees C, whereas other hemicellulases (beta-xylosidase, beta-glucosidase, and alpha-L-arabinofuranosidase) were produced at levels less than 7 nkat/ml. Cultivation on D-xylose yielded much lower levels of xylanase (350 nkat/ml), although other hemicellulase levels were similar to those produced on corn cobs. The influence of agitation rate and dissolved oxygen tension (DOT) on hemicellulase production was studied further in a bioreactor. On xylose, xylanase activities of 4,330 nkat/ml and 4,900 nkat/ml were obtained at stirrer speeds up to 1,400 rpm to control DOT. At a constant stirrer speed of 400 rpm, xylanase activities of 10,930 nkat/ml and 15,630 nkat/ml were obtained when cultivated on xylose and beechwood xylan respectively, despite DOT levels below 5% for the duration of fermentation. The results indicate that there is an interaction between agitation rate and DOT, impacting on xylanase and accessory enzyme production. Higher agitation rates favoured the production of xylosidase, arabinofuranosidase and glucosidase by T. lanuginosus strain SSBP, whereas the lower agitation rates favoured xylanase production. Rheological difficulties precluded cultivation on corn cobs in the bioreactor. Volumetric xylanase productivities of 1,060,000 nkat/l x h and 589,000 nkat/l x h obtained on beechwood xylan and xylose indicate that T. lanuginosus strain SSBP is a hyperxylanase producer with considerable industrial potential.
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PMID:The production of hemicellulases by Thermomyces lanuginosus strain SSBP: influence of agitation and dissolved oxygen tension. 1113 98