α-Mannosidases from suspension-cultured sugar beet cells

Abstract

The majority of intracellular α-mannosidase activity from suspension-cultured sugar beet cells was of vacuolar origin. Cell wall bound α-mannosidase was mostly extracted from purified cell wall after successive treatment with deoxycholate, saline and EDTA, commerical cellulase and pectinase. Soluble and cell wall bound α-mannosidase were purified separately to homogeneity. Soluble and cell wall α-mannosidases were nearly similar regarding profiles of activity with changing pH and temperature, K m value for p-nitrophenyl-α- d-mannoside, M r , and sensitivity to various metal ions and EDTA. Soluble α-mannosidase was composed of four different subunits ( M r , 72 000, 62 000, 57 000 and 34 000) and wall bound enzyme, three subunits ( M r , 72 000, 62 000 and 34 000). To compare α-mannosidase from dedifferentiated cells with that from differentiated cells, intracellular enzyme from mature roots was also purified to homogeneity. Both the intracellular α-mannosidase from mature roots and that from cultured cells exhibited similar behaviour during their purification and were nearly similar regarding some properties. The enzyme was composed of two different subunits ( M r , 72 000 and 34 000).