Organic solvent functional group effect on enzyme inactivation by the interfacial mechanism

We have used a bubble column apparatus to study interfacial inactivation of enzymes. The amount of enzyme inactivated was proportional to the area of organic solvent exposed, as is characteristic of the interfacial mechanism. Tests were made with a series of 12 solvents of log P close to 4.0, but wi th different functional groups. With alpha- and beta-chymotrypsin, inactiva tion was much less severe with amphiphilic molecules like decyl alcohol, th an with less polar compounds (heptane as the extreme case). This correspond s to a correlation with aqueous-organic interfacial tension, and presumably reflects a more polar interface as seen by the enzyme adsorbing from the a queous phase. A 50% mixture of decyl alcohol and heptane behaved similarly to pure decyl alcohol, which would be expected to accumulate at the interfa ce. With pig liver esterase, the correlation was rather weak, however. Accu mulated data for interfacial inactivation by alkanes was examined for the a bove enzymes, and also papain, trypsin, urease and ribonuclease. The differ ing sensitivities did not show a clear correlation with any enzyme property , although there was some relationship to adiabatic compressibility, therma l denaturation temperature and mean hydrophobicity. (C) 2000 Elsevier Scien ce B.V. All rights reserved.