ALPHA-GLUCURONIDASE IN 2 MICROBIAL XYLANOLYTIC SYSTEMS

The mode of action and some properties of the newly discovered fungal enzyme .alpha.-glucoronidase are described. The enzyme acts synergistically with xylanases and liberates 4-O-methyylglucuronic acid from 4-O-methylglucuronic acid-substituted xyloogligomers. .alpha.-Glucuronidase is readily produced by Agaricus bisporus and Pleurotus ostreatus, which are, however, poor producers of xylanases and .beta.-xylosidases. Comparative fermentations with different media showed (4-O-methylglucurono)-D-xylan from beechwood to be the best substrate and A. bisporus to be the more powderful organism. An enzyme test for .alpha.-glucuronidase activity has been developed. 2-O-(4-O-Methyl-.alpha.-D-glucopyranosyluronic acid)-D-xylobiose, which is neither degraded by xylanases nor by .beta.-xylosidases, was used as substrate. The uronic acid substituent was bound by an .alpha.-1,2 linkage to the non-reducing xylose residue. Anion exchange chromatography in acetate medium was a powerful tool for detection of degradation products.