title: Purification and biochemical characterization of an extracellular endoglucanase from the necrotrophic oomycete, Pythium myriotylum Dreschler.
abstract: An extracellular endoglucanase (EG) that catalyzes the hydrolysis of carboxy-methyl cellulose (CMC) as substrate was purified to homogeneity from the soft-rot causing oomycete P. myriotylum with maximum EG production observed in presence of 1% (w/v) sucrose. The enzyme designated PmEG was observed to be monomeric with a molecular weight of 78 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Optimal activity of PmEG was determined at pH 5.0 and 25 °C with stability observed at pH extending over acidic to alkaline ranges viz., 3.0-10.0 and thermal stability upto 75 °C for 1 h. Optimal PmEG activity was obtained by addition of metal ions viz., Ca(2+) , Fe(3+) , Zn(2+) , Cu(2+) , Al(3+) , and also in presence of DTT and β-mercaptoethanol while it was inhibited by Cr(2+) . Various organic solvents, surfactants, and the oxidant, H2 O2 had little/no effect on PmEG activity reflecting its robustness and potential commercial significance. Kinetic constants of PmEG, Km and Vmax were determined as 1.1 mM and 407 µmol min(-1)  mg(-1) protein, respectively. Glucose was observed to cause mixed non-competitive inhibition of PmEG.
authors.affiliation: School of Biotechnology, National Institute of Technology Calicut (NITC), Calicut, Kerala, India.
authors.forename: C
authors.initials: C
authors.lastname: Geethu
authors.forename: R Aswati
authors.initials: RA
authors.lastname: Nair
mesh_terms: D002480:Cellulase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011775:Pythium / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D002480:Cellulase
keywords: Carboxymethylcellulase; Endoglucanase; Extracellular; Oomycete; Pythium myriotylum