Isolation and characterization of an enzyme from the Greenshell™ mussel Perna canaliculus that hydrolyses pectenotoxins and esters of okadaic acid

Abstract

An enzyme capable of hydrolysing pectenotoxins (PTXs) and okadaic acid (OA) esters within the hepatopancreas of the Greenshell™ mussel Perna canaliculus was isolated and characterized. The enzyme was purified by sequential polyethylene glycol fractionation, anion exchange, hydrophobic interaction, gel filtration and hydroxyapatite chromatography. The enzyme was an acidic (pI ∼ 4.8), monomeric, 67 kDa, serine esterase with optimum activity at pH 8.0 and 25 °C. PTX2 and PTX1 were hydrolysed but the enzyme was inactive against PTX11, PTX6 and acid isomerised PTX2 and PTX11. PTX11 and PTX2b competitively inhibited PTX2 hydrolysis. The enzyme also hydrolysed short and medium chain length (C2–C10) 4-nitrophenyl-esters, okadaic acid C8–C10 diol esters and DTX1 7-O-palmitoyl ester (DTX3). MALDI-Tof MS/MS analysis showed that the enzyme had some homology with a juvenile hormone esterase from the Red Flour Beetle Tribolium castaneum, although BLAST searches of several data bases using de novo amino acid sequences failed to identify any homology with known proteins.