A-Amylase in aleurone protoplasts

GA4-17-S-propyl-S-phenacyl azide (structure I, Fig. 3) induces a-amylase in aleurone protoplasts (Fig. 1), although it is less active than the parent compound (GA4). In aqueous solution it has a X ax of294 nm (Fig. 2). Solutions are stable in the dark but are photolyzed within seconds of exposure to intense light of wavelengths above 300 nm (Fig. 2). Aryl azides photolyse to highly reactive aryl nitrenes that can covalently attach to amino acids at the binding site. See [15] for a detailed. account of the reactions of aryl nitrenes. 

The anti-idiotypic serum 455 2 inhibits GA4-induction of a-amylase in aleurone protoplasts (Table 5). This inhibition is of high titre and can be reversed by MAC 182, but not by pre-immune serum. Another anti-idiotypic serum, 455 1, behaves similarly but is of lower titre (data not presented). Both these sera will agglutinate aleurone protoplasts (Fig. 5), indicating that they probably recognize determinants at the protoplast surface which are involved in GA-perception. 

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