PURIFICATION AND CHARACTERIZATION OF AN ENDOXYLANASE FROM TRICHODERMA-KONINGII G-39

Trichoderma koningii G-39 produced xylanases in submerged culture using oat spelt xylan or crystalline cellulose, Avicel, as the sole carbon source. A low-M(r) xylanase was purified from the culture filtrate by ion-exchange chromatography on SP-Trisacryl-M and gel filtration on Fractogel TSK HW-50F. It was homogeneous on SDS/PAGE and isoelectric focusing. A typical procedure provided about 11-fold purification with 4.5 % protein yield and 50 % activity recovery. The purified enzyme has an M(r) value of about 21500 and a pI of 8.9. Its specific activity was 6100 units/mg of protein, with optimal activity towards 0.5 % xylan at about pH 5.5 and 60-degrees-C. The purified enzyme had no activity against CM-cellulose with a degree of substitution of 0.63. It also showed no beta-xylosidase activity. The K(m) and V(max.) values, as determined with the soluble fraction of oat spelt xylan as substrate, were 0.70 mg/ml and 1.85 x 10(6)mu-mol/min per mg of enzyme respectively. Hg2+ (1 mM) and SDS (10 mM) completely inhibited xylanase activity, whereas Ca2+ showed no significant effect on the enzyme activity at 1 mM, but gave 80 % inhibition at 10 mM. The enzyme contained about 4.4 % carbohydrate and showed an immunological relationship to a cellobiohydrolase from the same fungal strain.