CHARACTERIZATION OF ENDOGLUCANASES FROM THE BROWN-ROT FUNGI GLOEOPHYLLUM-SEPIARIUM AND GLOEOPHYLLUM-TRABEUM

Two endoglucanases (EGS and EGT) were isolated from the fungi Gloeophy llum sepiarium and Gloeophyllum trabeum, respectively, rising fraction ated ammonium sulfate precipitation hydrophobic interaction chromatogr aphy, and gel filtration. EGS and EGT had similar molecular masses (45 .1 kDa and 40.5 kDa) and pI values (3.8 and 3.1) and homolog N-termina l amino acid sequences (21 aa). Both enzymes were activated by Ca2+ an d Zn2+ and inhibited by heavy metal ions; however; EGS and EGT acted d ifferently on both soluble celluloses and dissolving pulp. Additionall y, only EGS was able to cleave galactoglucomannan. On carboxymethylcel lulose, EGS and EGT showed K-M values of 7.6 and 6.3 g l(-1) and K-cat values of 92.3 and 86.2 s(-1), respectively. Both enzymes had higher K-M and lower K-cat values on hydroxymethylcellulose. The EGS appeared to act more randomly on CMC and HEC and released larger oligomers fro m both acid swollen cellulose and dissolving pulp. When added to disso lving pulp in combination with hemicellulases, both of the endoglucana ses increased the amount of hemicellulose solubilized when compared to the hemicellulases alone, with EGS showing a more pronounced effect. (C) 1998 Elsevier Science Inc.