MODULATION OF A PROTEOLYTIC-ENZYME ACTIVITY BY MEANS OF A PHOTOCHROMIC INHIBITOR

On the basis of the known mechanism of the inhibition of a leaf protei nase by polycationic compounds we have synthesized a molecule in which two primary amino groups are spaced by an azobenzene moiety. The azo compound kept in the dark at room temperature is in the planar trans c onfiguration. The trans-cis photoisomerization cycle is accomplished b y irradiating the azo compound at 340 and 417 nm for the forward and b ack reactions respectively. The trans isomer was found to be a competi tive inhibitor of the proteinase, whereas the cis isomer in the same c oncentration range did not inhibit the enzyme. This could be attribute d to the different geometry and polarity of the two photoisomers. The modulation of the enzyme activity was recorded as a function of the ir radiation time of the azo compound at the two reported wavelengths for three successive cycles. No decay in the enzyme response was observed during the cycles, indicating the reversibility of the process.