SUBSTRATE-DEPENDENT ACTIVATION OF LATENT POTATO LEAF POLYPHENOL OXIDASE BY ANIONIC SURFACTANTS

Potato leaf polyphenol oxidase was purified with a 5-fold increase in specific activity and a recovery of 65% by using two sequential phase partitionings in Triton X-114. The second phase separation, which has never been used previously, increased both the purification rate and the removal of phenolic compounds until they were reduced to only 3 % of the original concentration with minimal loss in activity. The enzyme obtained was latent and was only activated by anionic surfactants (sodium dodecyl sulfate and dodecanesulfonic acid). The degree of activation depended on the pH and hydrophobicity of the substrate used and was highest for tert-butyl catechol (4-fold) and at pH 4.0, less for 4-methylcatechol (1.7-fold), and zero in the most hydrophilic substrate (chlorogenic acid). This activation also affected the kinetic constants, K(M) decreasing and V(max) increasing, thus resulting in a 4-fold increase in the catalytic efficiency for tert-butylcatechol and 1.5-fold increase for 4-methylcatechol.