Production, purification, and properties of an α- l-arabinofuranosidase from Cihomitus squalens

Abstract

A white-rot fungus Dichomitus squalens, when grown on 1% wheat-straw glucuronoarabinoxylan under aerated submerged conditions, secreted an α- l-arabinofuranosidase (4.3 nkat/mL). The enzyme was purified 70-fold by ammonium sulfate precipitation, chromatofocusing on PBE 94, gel filtration on Ultrogel AcA 54, rechromatofocusing on PBE 94, and lectin affinity chromatography on Concanavalin A-Ultrogel. The enzyme is a glycoprotein having a molecular weight of 60,000 and a pI of 5.1. The enzyme exhibited maximal activity at pH 3.5 and at 60°, and was fully inactivated within 30 min at 70°. The K m value for p-nitrophenyl α- l-arabinofuranoside was 1.64m m. The α- l-arabinofuranosidase liberated arabinose from sugar-beet arabinan, wheat-straw and oat-spelt arabinoxylans, and wheat-bran heteroxylan, and was inactive towards gum arabic.