Fractionation of the enzymes of the barley aleurone layer: Evidence for a soluble mode of enzyme release

Summary Aleurone cells of barley (Hordeum vulgare L.) contain microbodies as determined by histochemical localization with diaminobenzidine. These microbodies can be isolated from both water and gibberellic acid (GA₃) treated cells and identified on sucrose density gradients as glyoxysomes on the basis of their buoyant densities (1.25 g cm^-3) and their enzyme complement. Fractionation of aleurone layer homogenates by differential centrifugation after varying times of exposure to GA₃, however, does not indicate the presence of a discrete secretory vesicle containing either -amylase or -1,3-glucanase. Cytological evidence also suggests that at least -1,3-glucanase is not released from these cells by means of a discrete secretory vesicle.Supported by National Science Foundation Grant GB-27468. The assistance of Dr. William Breidenbach in the assay of glyoxysomal enzymes is gratefully acknowledged.