Hydrolysis of allylic phosphates by enzymes from the flavedo of Citrus sinensis

Abstract

Acid phosphatase activities have been partially purified from an aqueous extract of an acetone powder from orange flavedo. The use of a gel filtration step with an ionic gradient allowed a dissociation of proteins from pigments, thus facilitating purification and stabilization of the enzymes. The enzymes do not require metals for full activity, and they hydrolysed a wide spectrum of phosphorylated substrates. C 10–C 20 allylic pyrophosphates and monophosphates were hydrolysed sequentially by these ‘prenylphosphatases’. The final product was the corresponding unrearranged prenyl alcohol. This demonstrated the absence of E-Z isomerization and suggested an OP bond cleavage. Prenylphosphatases exhibited a certain degree of chain length specificity. Although the E or Z conformation of the C-2 double bond was not important, its presence was required for full activity. Excess prenylpyrophosphate inhibited the rate of formation of alcohols, most likely through the inhibition of phosphomonoesterase activity. These prenylphosphatases generated the alcoholic components of essential oils from the corresponding pyrophosphates and removed them from the chain lengthening process.