EFFECTS OF SOLVENTS AND SURFACE-ACTIVE AGENTS ON PLASTID PHOSPHATIDASE C ACTIVITY

Abstract

Large stimulations of plastid phosphatidase C activity were produced by (i) linear aliphatic ethers, ketones, and esters; (ii) mixtures of methanol with ethyl ether, petroleum ether, or benzene; and (iii) anionic detergents. Cyclic ethers, ketones, or esters and also alcohols, aldehydes, halogenated compounds, or hydrocarbons produced relatively small stimulations; cationic or non-ionic detergents produced little or no stimulation. The stimulations produced by linear aliphatic ethers, ketones, or esters varied greatly with the chain length of the hydrocarbon groups attached to the oxygen functional group: in each respective class, the most effective solvents were ethyl ether, n-propyl ketone, methyl pentyl ketone, ethyl butyrate, and butyl acetate. The most probable mechanism for explaining the stimulation effect is concluded to be one which involves adsorption of the stimulating solvents at the surfaces of the lecithin and plastid particles in a manner which makes these surfaces lipophilic and thus mutually attracting.In general water-insoluble solvents (ethers, ketones, esters, hydrocarbons) produced relatively little inactivation of enzymatic activity, while water-miscible solvents (alcohols, cyclic ethers, etc.) were strongly inactivating, especially at high concentrations (60–70%). Anionic detergents were not inhibitory in the concentration range in which they were stimulating (< 0.02 M), but were inhibitory at higher concentrations; cationic detergents were strongly inhibitory at all concentrations.It is concluded that extraction of plant phosphatides without concomitant enzymatic degradation should be possible by the use of i-propanol or n-propanol as solvent.