Characterization of Patatin Esterase Activity in AOT—Isooctane Reverse Micelles

Patatin is a family of glycoproteins that accounts for 30-40% of the total soluble protein in potato (Solanum tuberosum L.) tubers. This protein has been reported not only to serve as a storage protein but also to exhibit lipid acyl hydrolase (LAH) activity. In this study patatin is characterized in AOT-isooctane reverse micelles. The influence on the enzymatic activity of characteristic parameters of reverse micelles, Wo (= H2O/ AOT), and the percentage of H2O, were investigated. The results obtained show that patatin esterase activity varies with Wo but remains constant throughout the range of 0 values studied. The variation with Wo showed that the activity follows an S-shaped behavior pattern, reaching a maximum at about Wo = 20 for 2% H2O. Patatin esterase activity was compared with p-nitrophenyl (PNP) fatty acid esters of different chain lengths. The activity was much higher for PNP-caprylate. The pH optimum was 6.0, different from the value obtained when patatin esterase activity was measured in mixed micelle systems. The optimal temperature was 35 °C, above which the activity decreased to almost zero. The kinetic parameters were also evaluated (Km = 10 mM, Vm = 158 ~M/min, Vm/Km = 15.8 x 10^-3 min^-1). This paper shows the suitability of reverse micelles for measuring patatin esterase activity, since it allows the study of the enzyme in similar conditions to that prevailing in vivo.