A LIMITED SURVEY OF THE PHYLOGENETIC DISTRIBUTION OF POLYPHENOL OXIDASE

A variety of terrestrial and aquatic plant species were tested for the presence of polyphenol oxidase (PPO), using three different assay protocols. All aquatic green algae (Chlorella, Stigeoclonium, Microspora, Ulva and Spirogyra) tested have no detectable PPO except for a Trebouxioid alga (lichen symbiont), and Coleochaete. Of the Charalean algae Chara and Nitella, only the latter had measurable activity. Some hepatics (Conocephalum and Marchantia) possess the enzyme, but two species of Riccia tested do not. The anthocerotes Phaeoceros, Anthoceros and Notothylas have low, but easily detectable PPO. The mosses, Dicranum, Sphagnum and Thuidium, have no detectable activity. All of the ferns and fern allies tested have PPO activity. Among seed plants, PPO is undetectable in Ginkgo or any of the conifers tested. All but two species of the angiosperms surveyed possessed the enzyme. The M(r), as determined by semi-native electrophoretic mobility, ranged widely from 30 000 to 200 000, depending upon species. All species with PPO activity measured by spectrophotometric or gel assay had cytochemically-detected activity localized to the thylakoid membranes, with cytochemical product accumulating in the lumen of the thylakoid.