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A ß-1,4-endoxylanase from the ericoid mycorrhizal
fungus Hymenoscyphus ericae
poster
BURKE, RONALD M.1, & JOHN W. G.
CAIRNEY2
1Biochemistry and Applied Molecular Biology,
UMIST, PO Box 88, Manchester, M60 1QD, UK
2Biological Sciences, University of Western
Sydney, Nepean, PO Box 10, Kingswood, NSW 2747, Australia
ICOM1 Abstract
There has been much recent emphasis placed on the role of
proteases and phosphatases in the ericoid mycorrhizal
symbiosis. However, there is increasing evidence that
ericoid fungal endophytes also produce enzymes capable of
degrading the plant cell wall. Such activities are likely
to be significant in a number of ways, namely: in the
penetration of the wall of host cortical cells during
establishment of the ericoid mycorrhizal symbiosis; in the
exploitation of nutrients sequestered within plant cell
walls; and in the degradation of moribund plant material
during saprotrophic growth or symbiosis. Here we report the
purification to electrophoretic homogeneity of a ß-
1,4-endoxylanase (E.C.3.2.1.8) from H.ericae using
isoelectric focusing, ion exchange and gel permeation
chromatography. Physiochemical characterization of the
purified enzyme showed an isoelectric point of 4.85-5.20
and a molecular weight of 31.6kD. The enzyme has an
apparent S0.5 of 3.75 mg.ml-1 for
soluble birchwood arabinoxylan and a Vmax of 468.0
nkatal.(mg protein)-1. The pH optimum for
activity is 4.5 and that for stability is 3.5-4.0. These
values are discussed in the context of the ecology of H.
ericae.