Baker J E
United States Department of Agriculture, Agricultural Research Service, Agricultural Marketing Research Institute, Postharvest Plant Physiology Laboratory, Beltsville, Maryland 20705.
Plant Physiol. 1976 Nov;58(5):644-7. doi: 10.1104/pp.58.5.644.
The levels of superoxide dismutase (SOD) activity in extracts of preclimacteric apple, banana, avocado, and tomato fruits were not greatly different than in extracts of postclimacteric fruits. The results indicate that no major quantitative change in SOD occurs in fruits with or preceding the onset of senescence. Tomato fruit SOD was studied in more detail, and was found largely in the soluble fraction, and to a lesser extent in the mitochondrial and plastid fractions. The soluble fraction was purified by ammonium sulfate fractionation, column chromatography, and isoelectric focusing. Isoelectric focusing separated SOD from contaminating peroxidases. The purified tomato SOD showed an apparent molecular weight of 31,500 determined by gel filtration. Polyacrylamide gel electrophoresis of this preparation indicated two SOD components corresponding to two protein bands, one of which stained more intensely than the other. The purified tomato enzyme was inhibited 90% by 1 mm KCN.
在跃变前的苹果、香蕉、鳄梨和番茄果实提取物中，超氧化物歧化酶（SOD）的活性水平与跃变后果实提取物中的活性水平并无太大差异。结果表明，在衰老开始时或之前的果实中，SOD没有发生重大的定量变化。对番茄果实的SOD进行了更详细的研究，发现其主要存在于可溶部分，较少存在于线粒体和质体部分。通过硫酸铵分级沉淀、柱色谱和等电聚焦对可溶部分进行了纯化。等电聚焦将SOD与污染的过氧化物酶分离。通过凝胶过滤测定，纯化后的番茄SOD的表观分子量为31,500。该制剂的聚丙烯酰胺凝胶电泳显示有两个SOD组分，对应于两条蛋白带，其中一条染色比另一条更强烈。纯化后的番茄酶被1 mM KCN抑制了90%。
