HYDROLYSIS OF PARABENES BY EXTRACTS FROM DIFFERING LAYERS OF HUMAN SKIN

We could distinguish four carboxylesterases capable of hydrolyzing 4-h ydroxy-benzoic acid esters in human skin and subcutaneous fat tissue. The highest specific activities were found in an extract from subcutan eous fat tissue. The most prominent esterase of this tissue prefers th e methyl ester of 4-hydroxybenzoic ester (methyl parabene). Its activi ty decreases with increasing chain length of the alcohol moiety of the parabenes. The existence of a second parabene esterase in subcutaneou s fat is concluded from organophosphate inhibition characteristics. An other prominent parabene esterase was characterized in extracts from t ransformed keratinocytes. It prefers butyl parabene and its activity d ecreases with decreasing chain length of the alcohol moiety. The fourt h parabene esterase is an enzyme of blood which contaminates the tissu e extracts used here. All of the tissue extracts were active at pH 8.0 , no parabene hydrolyzing activity could be demonstrated at pH 5.0.