O-DEALKYLATION OF COUMARIN AND RESORUFIN ETHERS BY UNICELLULAR GREEN-ALGAE - KINETIC-PROPERTIES OF CHLORELLA-FUSCA AND CHLORELLA-SOROKINIANA

O-Dealkylations of resorufin and coumarin ethers, mediated by microsom al cytochrome P450 monooxygenases from animals, plants and microorgani sms, are shown here to be performed also by intact cells of the unicel lular green algae Chlorella fusca and Chlorella sorokiniana. The activ ity of the O-dealkylation of these ethers was up to tenfold higher wit h Chlorella sorokiniana. Both algae dealkylated methyl-, ethyl-, and p entylethers of resorufin and coumarin. Dealkylation in vivo indicated efficient absorption of methoxy- and ethoxyresorufin, confirmed by the respective absorption kinetics. Piperonylbutoxide and 1-aminobenzotri azole, known inhibitors of plant and mammalian cytochrome P450s, signi ficantly inhibited the O-dealkylase activity of both algal strains. Th e use of synchronized cultures of both algae revealed that efficiency of O-dealkylation depends on the stage of the cell cycle: during the g rowth phase, the O-dealkylase activities increased more than proportio nal, and the distinct drop in activity during the last hours of the li ght period indicated the appearance of an endogenous substrate.