Isolation and Purification of an α-Mannosidase from Coleoptiles of Avena sativa

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Abstract
An .alpha.-mannosidase was purified from the coleoptiles of A. sativa L. variety Segrehavre. The enzyme, which is tightly associated with the cell wall, was solubilized with 3 M LiCl. The purification involves precipitation with (NH4)2SO4, gel filtration, ion exchange chromatography and isoelectric focusing. The enzyme appears homogeneous when chromatographed on disc gels and on isoelectric focusing gels. The enzyme runs as a single protein of constant specific activity when chromatographed on Sephadex G-200. The estimated MW of the enzyme is 630,000. The enzyme appears to have no metal ion cofactor requirement and is insensitive to p-chloromercuribenzoate. The pH optimum for the enzyme with p-nitrophenyl-.alpha.-D-mannoside as the substrate is 4.5 and the Km is 3.2 mM. The enzyme may have some carbohydrate associated with it as indicated by a positive periodate-Schiff reaction on disc gels.