Characterization of cellulase complex of Streptomyces albaduncus.
Exoglucanase and endoglucanase (glucanases) enzymes of S. albaduncus were found to be very stable, showing only 36% and 8% loss in activities respectively after 3 days of incubation at 50 degrees C. In contrast, beta-glucosidase was significantly less stable retaining only 22.30% activity after 30 min incubation at 40 degrees C. The glucanases manifested maximum stability in pH range of 5.5-6.0 whereas beta-glucosidase was completely stable over a broad pH range of 6.5-9.0. Both glucanases were enhanced by some cations whereas beta-glucosidase did not require any cation for activity. K(m) values for crude exoglucanase, endoglucanase and beta-glucosidase were 40.00 mg/ml, 92.30 mg/ml and 1.714 mM with maximum reaction velocities (Vmax) of 0.606, 33.330 and 0.109 IU/mg of protein, respectively. The enzymes were subject to end-product inhibition, with exo- and endo-glucanases decreasing by 20% and 70% respectively, in the presence of 0.3% glucose. However, beta-glucosidase showed marked resistance to glucose inhibition, retaining 59% of residual activity even in the presence of 30% glucose in the reaction mixture. This characteristic may be advantageous in the commercial exploitation of enzyme system. An activation of beta-glucosidase at lower concentrations of glucose suggests competitive inhibition.
Harchand
R K
RK
Department of Microbiology, Guru Nanak Dev University, Amritsar, India.
Singh
S
S
D002412:Cations / Q000378:metabolism / Q000494:pharmacology; D002480:Cellulase / Q000378:metabolism*; D043366:Cellulose 1,4-beta-Cellobiosidase; D004492:Edetic Acid / Q000494:pharmacology; D043326:Glucan 1,3-beta-Glucosidase; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D006361:Heating; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013302:Streptomyces / Q000201:enzymology* / Q000378:metabolism; D001617:beta-Glucosidase / Q000378:metabolism*
D002412:Cations; D004492:Edetic Acid; D001617:beta-Glucosidase; D002480:Cellulase; D043326:Glucan 1,3-beta-Glucosidase; D043366:Cellulose 1,4-beta-Cellobiosidase; D005947:Glucose