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Isolation and Purification of an -Mannosidase from Coleoptiles of Avena sativa¹

^a Department of Biochemistry and Biophysics, University of California, Davis, California 95616

An -mannosidase has been purified from the coleoptiles of Avena sativa L. var. 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 molecular weight 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--D-mannoside as the substrate is 4.5 and the K_m is 3.2 mM. The enzyme may have some carbohydrate associated with it as indicated by a positive periodate-Schiff reaction on disc gels.

³ Deceased.

¹ This investigation was supported in part by Research Grant R800870 from the United States Environmental Protection Agency. Material submitted by L.C.G. was in partial fulfillment of the requirements for the Ph.D. in Biochemistry.