| 摘要 |
This invention relates to a composition comprising a substantially pure enzyme capable of degrading arabinoxylan and having a molecular weight of about 45,000. More preferably this invention relates to such an enzyme which has a pH optimum between about 6.5 to about 7.0. The enzyme is derived from bacteria capable of hydroloyzing plant cell wall material, preferably from Bacillus most preferably from Bacillus subtilis. This invention further relates to such a composition which is further capable of selectively dissociating feraxan from a maize cell wall preparation. Additionally, compositions of this invention are unable to degrade Rhodymenia (1->3),(1->4)- beta -D-xylan and larch arabino-(1->4)- beta -D-xylan. Compositions of the present invention are capable of releasing fragments in a maize cell wall preparation at the glycosidic linkages of C1 and C5 arabinofuranosyl; C1 of terminal arabinofuranosyl; C2 and C4 of xylopyranosyl; C3 and C4 of xylopyranosyl, C1 and C3 of xylopyranosyl and C1 of terminal glucuronosyl. Compositions contemplated by the invention are also capable of releasing 2,4/3,4-linked-xylopyranosyl, terminal-arabinofuranosyl, 5-linked-arabinofuranosyl, 4-linked-xylopyranosyl, terminal-glucurono-pyranosyl and esterified ferulic acid from maize arabinoxylan. These compositions are preferably prepared from crude Bacillus sp. extracts by using a purification step selected from at least one of the following steps: differential precipitation using salts, ionic exchange chromatography, molecular filtration, HPLC, ultrafiltration and diafiltration.
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