Department of Life Science and Biotechnology, University of Ferrara, Ferrara, Italy.
Council for Agricultural Research and Economics, Research Centre for Olive, Citrus and Tree Fruit, Fruit Research Unit, Forlì, Italy.
J Sci Food Agric. 2019 Mar 15;99(4):1795-1803. doi: 10.1002/jsfa.9372. Epub 2018 Oct 29.
In peach fruit, carotenoid accumulation in the mesocarp causes the difference between yellow and white genotypes. The latter are generally characterized by a peculiar and more intense aroma, because of higher release of volatiles deriving from dioxygenase-catalysed breakdown of the tetraterpene skeleton. The rate of carotenoid oxidation was investigated in peach (Prunus persica L.) fruits harvested at various stages of development. Two couples of white and yellow-fleshed isogenic varieties and an ancestral white-fleshed genotype were analysed, which had previously shown to differ in Carotenoid Cleavage Dioxygenase 4 allelic composition resulting in various combinations of putatively active/inactive proteins.
Carotenoid bleaching activity was localized in the insoluble fraction of fruit flesh chromoplasts. Higher rates of trans-β-apo-8'-carotenal than β-carotene bleaching suggest that the first cleavage reaction is the rate-limiting step. Consistently, HPLC analysis did not show the appearance of coloured intermediates in reaction mixtures. High levels of substrate breakdown were found during the initial phases of fruit development in all genotypes examined, whereas significant differences were evident during the second exponential growth phase and ripening onset. Also, the ratio of carotene versus carotenale utilization varied significantly.
Pattern comparison among activity levels measured in vitro on chromoplast enriched fractions suggests that cleavage enzyme(s) other than Carotenoid Cleavage Dioxygenase 4 play a significant role in carotenoid breakdown during fruit development and ripening. © 2018 Society of Chemical Industry.
在桃果实中，有色体中类胡萝卜素的积累导致了黄白两型品种的差异。后者通常具有独特而更强烈的香气，因为四萜骨架经加氧酶催化分解后，挥发性物质的释放量更高。本研究调查了不同发育阶段采收的桃果实中类胡萝卜素氧化的速率。分析了两对白肉和黄肉同型品种以及一个先前表现出不同的类胡萝卜素裂解双加氧酶 4 等位基因组成的白肉祖先基因型，这导致了潜在活性/非活性蛋白的各种组合。
类胡萝卜素漂白活性定位于果肉质体的不溶性部分。反式-β-apo-8'-胡萝卜素比β-胡萝卜素漂白的速率更高，这表明第一次裂解反应是限速步骤。一致地，HPLC 分析未显示反应混合物中有色中间体的出现。在所有被检测的基因型中，在果实发育的初始阶段发现了高水平的底物分解，但在第二指数生长阶段和成熟开始时则存在显著差异。此外，类胡萝卜素与胡萝卜素利用的比例也有显著差异。
在富含质体的级分上进行的体外活性测量的模式比较表明，在果实发育和成熟过程中，除了类胡萝卜素裂解双加氧酶 4 以外，其他裂解酶也在类胡萝卜素分解中发挥了重要作用。© 2018 英国化学学会。
