Ascorbate oxidase (AAO, EC 1.10.3.3) is a complex blue copper-protein capable to reduce molecular oxygen to water without generating reactive oxygen intermediates, by using ascorbic acid (AA) as an electron donor. We detected higher AAO activity when O2 concentration was experimentally increased in vivo, whereas AA concentration did not affect AAO activity. A rise in AAO activity also occurred in illuminated leaf disks. DCMU largely prevented light-dependent stimulation of enzyme activity. AAO activity was absent in the parasitic non-green plant Cuscuta reflexa. Taken together, our data strongly suggest that AAO up-regulation induced by O2 and light could have a fundamental role in regulating dioxygen diffusion in leaves performing dioxygenic photosynthesis.
In vivo elicitation of ascorbate oxidase activity by dioxygen and its possible role in photosynthesizing leaves
De Tullio M.Writing – Original Draft Preparation
2003-01-01
Abstract
Ascorbate oxidase (AAO, EC 1.10.3.3) is a complex blue copper-protein capable to reduce molecular oxygen to water without generating reactive oxygen intermediates, by using ascorbic acid (AA) as an electron donor. We detected higher AAO activity when O2 concentration was experimentally increased in vivo, whereas AA concentration did not affect AAO activity. A rise in AAO activity also occurred in illuminated leaf disks. DCMU largely prevented light-dependent stimulation of enzyme activity. AAO activity was absent in the parasitic non-green plant Cuscuta reflexa. Taken together, our data strongly suggest that AAO up-regulation induced by O2 and light could have a fundamental role in regulating dioxygen diffusion in leaves performing dioxygenic photosynthesis.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
