CELLULOSE-BINDING DOMAINS AND LINKER SEQUENCES POTENTIATE THE ACTIVITY OF HEMICELLULASES AGAINST COMPLEX SUBSTRATES

To evaluate the role of the CBDs and linker sequences in Pseudomonas x ylanase A (XYLA) and arabinofuranosidase C (XYLC), the catalytic activ ity of derivatives of these enzymes, lacking either the linker sequenc es or CBDs, was assessed. Removal of the CBDs or linker sequences did not affect the activity of either XYLA or XYLC against soluble arabino xylan, while derivatives of XYLA, in which either the CBD or interdoma in regions had been deleted, exhibited decreased activity against the xylan component of cellulose/hemicellulose complexes. Although a trunc ated derivative of XYLC (XYLC'''), lacking its CBD, was less active th an the full-length enzyme against plant cell wall material containing highly substituted arabinoxylan, XYLC''' was more active than XYLC on complex substrates where the degree of substitution of arabinoxylan wa s very low. These data indicate that CBDs and linker sequences play an important role in the activity of hemicellulases against plant cell w alls and other cellulose/hemicellulose complexes. (C) 1997 Elsevier Sc ience B.V.