α- d-Galactosidase activity and galactomannan and galactosylsucrose oligosaccharide depletion in germinating legume seeds

Abstract

Germinating seeds of lucerne, guar, carob and soybean initially depleted raffinose series oligosaccharides and then galactomannan. This depletion was accompanied by a rapid increase and then a decrease in α-galactosidase levels. Lucerne and guar contained two α-galactosidase activities, carob three and soybean four. One of these in each plant, from its location in the endosperm, time of appearance and kinetic behaviour, appeared to be primarily involved in galactomannan hydrolysis. This enzyme in lucerne had MW of 23 000 and could not be separated from β-mannanase by (NH 4) 2SO 4 fractionation, DEAE, CM or SE-cellulose chromatography or gel filtration, but only by polyacrylamide gel electrophoresis. In guar, carob and soybean, it could be separated by ion-exchange chromatography and gel filtration. In lucerne, carob and guar most of the total increase in activity was due to this enzyme. The other α-galactosidases had MWs of about 35 000 and could be separated from β-mannanase by dissection, ion exchange cellulose chromatography and gel filtration. They were located in the cotyledon-embryo and appeared to be primarily involved in galactosylsucrose oligosaccharide hydrolysis.