Characterization of wax-ester hydrolase from roots of white mustard (Sinapis alba L.) seedlings

The activity of wax-ester hydrolase in roots of white mustard (Sinapis alba L.) seedlings is located in a membranous fraction sedimenting at 15000 g. The enzyme which shows a high degree of hydrophobicity was solubilized with a synthetic detergent Triton X-100 and purified about 70-fold by acetone precipitation and gel permeation chromatography on Sepharose 6B. The purified enzyme preparation was active within a broad pH range of 5.8-8.5. Hydrolase activity with hexadecanyl palmitate as the substrate was stimulated by Triton X-100 and dithioerythritol. Of wax esters containing saturated fatty acids C2-C22 and saturated, primary alcohols C2-C24 the highest rate of hydrolysis was found with the esters containing palmitic acid (C16) and tetradecanol (C14). Data presented suggest that wax esters and steryl esters are either hydrolyzed by different specific enzymes or that two enzymes are present of different specificity towards the two substrates.