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In a recent paper Eberhart and Beck (4) suggested that the aryl-,β-glucosidase of Neurospora conidia is a mural enzyme. Similarly, Nevins (11) reported that ,β-glucosidase is strongly associated with cell walls during extraction of bean hypocotyls at pH 4.6 and suggested that this enzyme is wall-bound in situ, and Keegstra and Albersheim (9) noted that β-glucosidase could be effectively washed from the surface of sycamore cells grown in liquid culture. On the basis of histochemical evidence, Ashford (1) suggested that β-glucosidase in corn roots is associated with a reticulate network of strands and particles, and Ashford and McCully (2) concluded that this network is located peripherally in the cells.
Sweetclover homogenates contain a β-glucosidase which hydrolyzes the β-glucoside of cis-o-hydroxycinnamic acid (cis-o- HCA) (10). Under acidic conditions the aglycone lactonizes spontaneously, forming coumarin. The sweetclover enzyme also can hydrolyze the commonly used aryl-β-glucosidase substrate, PNP-G (12).
This report deals with the distribution of β-glucosidase activity in fractionated homogenates of sweetclover leaves and bean hypocotyls prepared under various conditions. The data presented indicate that binding to cell walls is not the only factor involved in determining these distribution patterns.