Arabinoxylan biosynthesis:: Identification and partial characterization of β-1,4-xylosyltransferase from wheat

The biosynthesis of arabinoxylan was investigated using microsomal membranes isolated from wheat seedlings. Incubation of the microsomes with UDP-[C-14]-D-xylose resulted in incorporation of radioactivity into polymeric product. Incorporation reached a maximum at day 3 during development of the seedlings. Treatment of the radiolabeled product with Aspergillus niger xylanase A released about 70% of the radioactivity to a 65% ethanol-soluble fraction. The released radioactivity was shown to be in the form of xylobiose, xylotriose and xylotetraose, which are the expected hydrolysis products of endo-xylanases. The synthesized xylan had an apparent molecular mass larger than 500 kDa.