琯溪蜜柚果实采后有机酸代谢

Study on the post-harvest metabolism of organic acids in fruit of Guanxi-miyou pomelo cultivar

以琯溪蜜柚果实为材料,测定了果实采后贮藏过程中的有机酸含量及相关代谢酶——柠檬酸合成酶(CS)、磷酸烯醇式丙酮酸羧化酶(PEPC)与细胞质乌头酸酶和NAD-异柠檬酸脱氢酶复合酶(NAD-IDH/Cyto-Aconitase)的活性,并探讨它们之间的相关性及有机酸的代谢机理。结果表明,1)琯溪蜜柚果实采后室温贮藏,果肉出现酸化,主要表现为柠檬酸含量大幅度增加,采后70 d达最高值,之后逐渐下降。相关分析表明,果实中的柠檬酸含量与CS活性呈极显著正相关,且与NAD-IDH/Cyto-Aconitase活性呈显著负相关。2)果实采后低温(6℃)贮藏,果实中的柠檬酸含量总体呈下降趋势,柠檬酸含量与PEPC活性呈极显著正相关。研究认为,CS、PEPC和NAD-IDH/Cyto-Aconitase是琯溪蜜柚果实采后有机酸积累的关键酶;果实采后低温(6℃)贮藏,可以较好地克服果实采后酸化的问题。

The contents of organic acids and the activities of organic acid-metabolizing enzymes,including citrate synthase（CS）,phosphoenolpyruvate carboxylase（PEPC）,Cyto-Aconitase（Cyto-Aconitase）and NAD-isocitrate dehydrogenase（NAD-IDH）were measured in the fruit of Guanxi-miyou pomelo cultivar after harvest and probed their interrelationships and the mechanism of the organic acid metabolism.The results showed that the fruit went sour when stored at room temperature.The citric acid in the fruit greatly accumulated and peaked 70 days after harvest and then declined slightly.Correlation anal-ysis showed that a significant positive correlation was observed between the content of citric acid and the activity of CS,while there was a significant negative correlation between the content of citric acid and the activity of NAD-IDH/ Cyto-Aconitase.Storing at low temperature of 6 ℃,the content of citric acid in the fruit declined on the whole.The content of citric acid had a significant positive correlation with the activity of PEPC.It is suggested that CS,PEPC and NAD-IDH/ Cyto-Aconitase were the main enzymes in organic acid accumulation of Guanxi-miyou pomelo fruit.We concluded that storing at low temperature of 6 ℃ could effectively solve the problems of the fruit acidification after harvest.