The reactions of ozone with proteins and unsaturated fatty acids in reverse micelles

Sodium oleate cosolubilized with lysozyme in reverse micellar solutions is shown to inhibit the ozone-mediated oxidation of tryptophan residues in the protein. The magnitude of inhibition by oleate, which is an indirect measure of the fraction of ozone that reacts with oleate instead of the protein, is predictable using a kinetic model that is based on the concentrations and the reactivities toward ozone of the amino acid residues in lysozyme and the double bond in oleate. Oleate (2 mM), linoleate (1 mM), linolenate (0.67 mM), and gamma-linolenate (0.67 mM) all inhibit the ozonation of lysozyme similarly; this indicates that ozone reacts with double bonds in mono-, di-, or polyunsaturated fatty acids at approximately the same rate. All these fatty acids reside at the micellar interface with their head groups facing inward toward the dispersed water pools and the hydrocarbon tails projecting into the bulk, continuous organic phase. Various short-chain 2-, 3-, and 4-alkenoic acids that reside predominantly in the water pools, and long-chain alkenes that reside in the bulk organic solvent, have a similar inhibitory effect on the ozone-mediated oxidation of tryptophan residues in lysozyme. Thus, the location of olefinic compounds in the micelles or bulk organic phase per se does not influence the rate of reaction in this reverse micellar system. A number of proteins that reside in the water pools of reverse micelles are found to behave similarly to lysozyme, including albumin, carbonic anhydrase, beta-casein, alpha-chymotrypsin, alpha-lactalbumin, beta-lactoglobulin, papain, apotransferrin, trypsin, and trypsin inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)