PHOTOPEROXIDATION IN ISOLATED CHLOROPLASTS .I. KINETICS AND STOICHIOMETRY OF FATTY ACID PEROXIDATION
PHOTOPEROXIDATION IN ISOLATED CHLOROPLASTS .I. KINETICS AND STOICHIOMETRY OF FATTY ACID PEROXIDATION
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DOI：
10.1016/0003-9861(68)90654-1
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发表时间：
1968-01-01
影响因子：
3.9
通讯作者：
PACKER, L
中科院分区：
文献类型：
--
作者：
HEATH, RL;PACKER, L
本文报道了离体叶绿体中光诱导的环化过氧化反应。在渗透缓冲介质中，叶绿体在光照下产生丙二醛（MDA）[长破折号]，这是三不饱和脂肪酸氢过氧化物的分解产物[长破折号]漂白内源叶绿素，并消耗氧气。这些过程表明：无光照时无反应;光照10-20分钟后的初始滞后期;速率与光强度平方根成比例的线性期;光照停止后3分钟内反应停止;光照数小时后终止期。上述过程的动力学符合循环过氧化方程，其速率系数接近化学过氧化。MDA/O_2 = 0.02和O_2/Chlbleached = 6.9的化学计量与其它生物系统中的MDA产生效率以及与不饱和脂肪酸与叶绿素的摩尔比相关。滞后相和线性相的活化能分别为17和0千卡/摩尔，与自氧化相同。在氧吸收的线性阶段期间，对温度和O2浓度的依赖性表明，在反应期间，在过氧化位点处的氧张力比在水相中低100倍。它的结论是，孤立的叶绿体在光照下可以进行循环的过氧化开始由叶绿素吸收的光。光过氧化导致叶绿体膜的叶绿素和三不饱和脂肪酸的破坏。
A photo-induced cylcic peroxidation in isolated chloroplasts is described. In an osmotic buffered medium, chloroplasts upon illumination produce malondialdehyde (MDA)[long dash]a decomposition product of tri-unsaturated fatty acid hydroperoxides[long dash]bleach endogenous chlorophyll, and consume oxygen. These processes show: no reaction in the absence of illumination; an initial lag phase upon illumination of 10-20 min. duration; a linear phase in which the rate is proportional to the square root of the light intensity; cessation of reaction occurring within 3 min. after illumination ceases; and a termination phase after several hours of illumination. The kinetics of the above processes fit a cyclic peroxidation equation with velocity coefficients near those for chemical peroxidation. The stoichiometry of MDA/O2 = 0.02, and O2/Chlbleached = 6.9 correlates well with MDA production efficiency in other biological systems and with the molar ratio of un-saturated fatty acids to chlorophyll. The energies of activation for the lag and linear phases are 17 and 0 kcal/mole, respectively, the same as that for autoxidation. During the linear phase of oxygen uptake the dependence upon temperature and O2 concentration indicates that during the reaction, oxygen tension at the site of peroxidation is 100-fold lower than in the aqueous phase. It is concluded that isolated chloroplasts upon illumination can undergo a cyclic peroxidation initiated by the light absorbed by chlorophyll. Photoperoxidation results in a destruction of the chlorophyll and tri-unsaturated fatty acids of the chloroplast membranes.