Effect of Compounds of Aryloxyaminopropanol Type on the Photosynthetic Activity ofSpinach Chloroplasts

Overview

The effect of 18 compounds of the aryloxyaminopropanol type – potencial beta-adrenolytics (differingeach from other by modifications in the hydrophilic and lipophilic part of the molecule) on theinhibition of oxygen evolution rate in spinach chloroplasts has been investigated. The compoundswith n-octyloxymethyl and n-nonyloxymethyl group in position 3 of aromatic ring were found toexhibit the highest inhibitory activity (IC50 = 67, resp. 120 mmol dm -3 ). The compounds containinga heterocycle or the dimethylamino group in the hydrophilic part of the molecule and withpropoxymethyl group on the aromatic ring were not active. Using EPR spectroscopy it was foundthat the studied compounds interact with Z + /D + intermediates, i.e. tyrosine radicals TyrZ and TyrDsituated in D1 and D2 proteins on the donor side of photosystem 2. Higher concentrations of thestudied inhibitors cause release of Mn 2+ ions from the oxygen evolving complex which is situated inphotosystem 2. The interaction of the tested compounds with chlorophyll occurring in the photo-synthetic centres has been confirmed by fluorescence measurements as well.

Key words:
aryloxyaminopropanols – beta-adrenolytics – photosynthesis – EPR spectroscopy –spinach