Purification and characterization of prophenoloxidase from cotton bollworm, Helicoverpa armigera

Abstract

Phenoloxidases are oxidative enzymes, which play an important role in both cell mediated and humoral immunity. Purification and biochemical characterization of prophenoloxidase from cotton bollworm, Helicoverpa armigera (Hübner) were carried out to study its biochemical properties. Prophenoloxidase consists of a single polypeptide chain with a relative molecular weight of 85kDa as determined by SDS-PAGE, MALDI-TOF MS and LC-ESI MS. After the final step, the enzyme showed 71.7 fold of purification with a recovery of 49.2%. Purified prophenoloxidase showed high specific activity and homology with phenoloxidase subunit-1 of Bombyx mori and the conserved regions of copper binding (B) site of phenoloxidase. Purified prophenoloxidase has pH optima of 6.8 and has high catalytic efficiency towards the dopamine as a substrate in comparison to catechol and L-Dopa. The PO activity was strongly inhibited by phenylthiourea, thiourea, dithiothreitol and kojic acid. © 2012 The Authors Entomological Research © 2012 The Entomological Society of Korea and Wiley Publishing Asia Pty Ltd.