Olive (Olea europaea) fruit contains high amounts of tocopherols that are responsible, along with secoiridoid phenolic compounds, for most of the antioxidant and anti-inflammatory properties of virgin olive oil. This study focuses on the molecular and biochemical characterization of olive 4-hydroxyphenyl pyruvate dioxygenase (OeHPPD) catalyzing the biosynthesis of homogentisic acid, which constitutes the phenolic residue in the tocopherol molecule. OeHPPD is a cytoplasmic enzyme with a molecular weight of 49.8 kDa and a predicted tertiary structure very similar to the Arabidopsis enzyme that suggests similar catalytic mechanisms. OeHPPD has an estimated K_cat of 75.26 s^–1 and catalytic efficiency (K_m/K_cat) of 0.145 μM^–1 s^–1 with 4-hydroxyphenyl pyruvate as the substrate. The expression analysis in fruits from selected olive cultivars harvested at different ripening stages indicates that the OeHPPD gene is temporally regulated and cultivar-dependent. Moreover, the analysis of OeHPPD expression in fruits affected by drought stress suggests that HPPD is involved in olive environmental adaptation.

中文翻译：

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参与初榨橄榄油中存在的生育酚生物合成的橄榄 4-羟基苯基丙酮酸双加氧酶的分子和生化表征


橄榄 （Olea europaea） 果实含有大量的生育酚，这些生育酚与类 secoiridoid 酚类化合物一起，是初榨橄榄油的大部分抗氧化和抗炎特性的原因。本研究侧重于橄榄 4-羟基苯基丙酮酸双加氧酶 （OeHPPD） 催化酪氨酸的生物合成的分子和生化表征，同质酸构成了生育酚分子中的酚类残基。OeHPPD 是一种细胞质酶，分子量为 49.8 kDa，预测的三级结构与拟南芥酶非常相似，表明具有相似的催化机制。以 4-羟基苯基丙酮酸为底物，OeHPPD 的估计 K_cat 为 75.26 s^–1，催化效率 （K_m/K_cat） 为 0.145 μM^–1 s^–1。在不同成熟阶段收获的选定橄榄品种果实中的表达分析表明，OeHPPD 基因受时间调控且依赖于栽培品种。此外，对受干旱胁迫影响的水果中 OeHPPD 表达的分析表明，HPPD 参与橄榄环境适应。