Caiola Maria Grilli, Canini Antonella
Department of Biology, University of Rome, 'Tor Vergata', Via della Ricerca Scientifica - 00133 Rome, Italy.
New Phytol. 1993 Oct;125(2):361-366. doi: 10.1111/j.1469-8137.1993.tb03887.x.
Superoxide dismutase (SOD) converts superoxide radicals into hydrogen peroxide and molecular oxygen and therefore represents the primary defence against oxygen damage. Using antibodies against Anabaena cylindrica Lemm. iron-SOD, the isoenzyme was localized by immunogold labelling in vegetative cells, heterocysts and akinetes of the cyanobacterium Anabaena cylindrica grown at different light intensities. At a low photon irradiance (25 μmol photons m s ), the density of iron-SOD labelling was similar in vegetative cells and in heterocysts, whereas in akinetes only 60 % of the gold particles were present as compared with the other cell types. At a higher photon irradiance (140 μmol photons m S ), iron-SOD labelling increased by 100% in both vegetative cells and in heterocysts but did not change in akinetes. The cultures grown at the photon irradiance of 140 μmol photons m s showed a rate of photosynthetic oxygen evolution 40 % higher than that of cultures grown at the lower photon irradiance. The increase of SOD labelling in vegetative cells is in line with the increased photosynthetic oxygen evolution induced by light. The unchanged SOD labelling observed in the akinetes suggests that light intensity does not seem to affect the oxidative metabolism due to respiratory activity.
超氧化物歧化酶（SOD）将超氧自由基转化为过氧化氢和分子氧，因此是抵御氧损伤的主要防线。使用针对圆柱鱼腥藻铁-SOD的抗体，通过免疫金标记将该同工酶定位在不同光照强度下生长的圆柱鱼腥藻的营养细胞、异形胞和厚壁孢子中。在低光子辐照度（25 μmol光子·m⁻²·s⁻¹）下，营养细胞和异形胞中铁-SOD标记的密度相似，而与其他细胞类型相比，厚壁孢子中仅存在60%的金颗粒。在较高光子辐照度（140 μmol光子·m⁻²·s⁻¹）下，营养细胞和异形胞中铁-SOD标记均增加了100%，但厚壁孢子中没有变化。在140 μmol光子·m⁻²·s⁻¹的光子辐照度下生长的培养物的光合放氧速率比在较低光子辐照度下生长的培养物高40%。营养细胞中SOD标记的增加与光照诱导的光合放氧增加一致。在厚壁孢子中观察到的SOD标记不变表明光照强度似乎不影响由呼吸活动引起的氧化代谢。
