Phenoloxidase of peach (Prunus persica) endocarp: Its relationship with peroxidases and lignification

A preliminary characterization of a phenoloxidase from extracts of soluble and ionically‐bound cell wall proteins of peach (Prunus persica L. Batsch, cv. Redhaven) endocarp is described in the present study to establish differences with peroxidases from the same plant tissue. The phenoloxidase activity was detected mainly in the first stage of peach fruit growth, while peroxidase activity and lignin content increased along the second stage of growth. There were clear differences between the two enzymes. The phenoloxidase had a pI value of 5.6, different from those of peroxidases isoenzymes with various pIs ranging from 3.6 to 9.6. The oxidase molecular mass was 112 kDa, similar to other phenoloxidases described in the literature, while all peroxidase isoenzymes showed a molecular mass of around 40 kDa. The specific activities of phenoloxidase against different substrates and its inhibition by various effectors suggest that the endocarp oxidase described here is probably a metal‐dependent polyphenol oxidase, displaying attributes of both catechol oxidase (EC 1.10.3.1) and laccase (EC 1.10.3.2).