Enzymic activities and galactomannan mobilisation in germinating seeds of fenugreek (Trigonella fœnum-graecum L. Leguminosae) : Secretion of α-galactosidase and β-mannosidase by the aleurone layer.
The activities of α-galactosidase, β-mannosidase and α-mannosidase were determined in extracts from the endosperm and from the embryo of fenugreek seeds at different stages of germination. Endosperm homogenates contained little or no activity of the above enzymes in the early stages of germination, before the reserve galactomannan began to be mobilised. The onset of galactomannan breakdown coincided with the appearance of α-galactosidase and β-mannosidase activities, which increased throughout the period of galactomannan degradation and then remained constant. A similar rise in α-galactosidase and β-mannosidase activities occurred during galactomannan breakdown in dry-isolated endosperms incubated under germination conditions. The increase could be suppressed by metabolic inhibitors which also inhibit galactomannan breakdown. Embryo homogenates contained high α-galactosidase, high α-mannosidase and some β-mannosidase activity at all stages of germination.No "oligomannosyl β-1,4 phosphorylase" activity could be detected either in the endosperm or in the embryo.It is concluded that the galactomannan of fenugreek is broken down by a series of hydrolases secreted by the aleurone layer of the endosperm. They include α-galactosidase, β-mannosidase and probably also endo-β-mannanase.
Institut für botanische Biologie und Phytochemie der Universität, Freiburg, Switzerland.
J S
JS
Grant Reid
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Meier