Institute of Biological, Environmental and Rural Sciences, Aberystwyth University , Gogerddan, Aberystwyth, Ceredigion SY23 3EE, Wales, U.K.
J Agric Food Chem. 2013 Aug 7;61(31):7421-30. doi: 10.1021/jf401122d. Epub 2013 Jul 24.
Polyphenol oxidase (PPO) genes and their corresponding enzyme activities occur in many plants; natural PPO substrates and enzyme/substrate localization are less well characterized. Leaf and root PPO activities in Arabidopsis and five legumes were compared with those of high-PPO red clover ( Trifolium pratense L.). Red clover PPO enzyme activity decreased leaves > stem > nodules > peduncle = petiole > embryo; PPO1 and PPO4 genes were expressed early in leaf emergence, whereas PPO4 and PPO5 predominated in mature leaves. PPO1 was expressed in embryos and nodules. PPO substrates, phaselic acid and clovamide, were detected in leaves, and clovamide was detected in nodules. Phaselic acid and clovamide, along with caffeic and chlorogenic acids, were suitable substrates for PPO1, PPO4, and PPO5 genes expressed in alfalfa ( Medicago sativa L.) leaves. PPO enzyme presence and activity were colocalized in leaves and nodules by cytochemistry. Substrates and PPO activity were localized in developing squashed cell layer of nodules, suggesting PPO may have a developmental role in nodules.
多酚氧化酶（PPO）基因及其相应的酶活性存在于许多植物中；天然 PPO 底物和酶/底物定位的特征还不太清楚。比较了拟南芥和 5 种豆科植物的叶片和根 PPO 活性与高 PPO 红三叶草（Trifolium pratense L.）的活性。红三叶草 PPO 酶活性在叶片中下降>茎>根瘤>花梗=叶柄>胚；PPO1 和 PPO4 基因在叶片出现早期表达，而 PPO4 和 PPO5 在成熟叶片中占优势。PPO1 在胚和根瘤中表达。在叶片中检测到 phaselic 酸和 clovamide，在根瘤中检测到 clovamide。phaselic 酸和 clovamide 以及咖啡酸和绿原酸是在紫花苜蓿（Medicago sativa L.）叶片中表达的 PPO1、PPO4 和 PPO5 基因的合适底物。细胞化学法将 PPO 酶的存在和活性在叶片和根瘤中进行共定位。在根瘤发育的压扁细胞层中定位了底物和 PPO 活性，表明 PPO 可能在根瘤中有发育作用。
