Simmondsia chinensis (jojoba) is the only plant known to store wax esters instead of triacylglycerols in its seeds. Wax esters are composed of very-long-chain monounsaturated fatty acids and fatty alcohols and constitute up to 60% of the jojoba seed weight. During jojoba germination, the first step of wax ester mobilization is catalyzed by lipases. To date, none of the jojoba lipase-encoding genes have been cloned and characterized. In this study, we monitored mobilization of storage reserves during germination of jojoba seeds and performed detailed characterization of the jojoba lipases using microsomal fractions isolated from germinating seeds. During 26 days of germination, we observed a 60–70% decrease in wax ester content in the seeds, which was accompanied by the reduction of oleosin amounts and increase in glucose content. The activity of jojoba lipases in the seed microsomal fractions increased in the first 50 days of germination. The enzymes showed higher activity towards triacylglycerols than towards wax esters. The maximum lipase activity was observed at 60 °C and pH around 7 for triacylglycerols and 6.5–8 for wax esters. The enzyme efficiently hydrolyzed various wax esters containing saturated and unsaturated acyl and alcohol moieties. We also demonstrated that jojoba lipases possess wax ester-synthesizing activity when free fatty alcohols and different acyl donors, including triacylglycerols and free fatty acids, are used as substrates. For esterification reactions, the enzyme utilized both saturated and unsaturated fatty alcohols, with the preference towards long chain and very long chain compounds. In in vitro assays, jojoba lipases catalyzed hydrolysis of triacylglycerols and different wax esters in a broad range of temperatures. In addition, the enzymes had the ability to synthesize wax esters in the backward reaction. Our data suggest that jojoba lipases may be more similar to other plant lipases than previously assumed.

中文翻译：

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发芽荷荷巴种子的脂肪酶有效水解甘油三酯和蜡酯并显示蜡酯合成活性

Simmondsia chinensis（荷荷巴油）是已知的唯一一种在其种子中储存蜡酯而不是甘油三酯的植物。蜡酯由超长链单不饱和脂肪酸和脂肪醇组成，占荷荷巴种子重量的 60%。在荷荷巴发芽过程中，蜡酯动员的第一步是由脂肪酶催化的。迄今为止，尚未克隆和表征任何荷荷巴脂酶编码基因。在这项研究中，我们监测了荷荷巴种子发芽过程中储存储备的调动，并使用从发芽种子中分离的微粒体部分对荷荷巴脂肪酶进行了详细的表征。在 26 天的发芽过程中，我们观察到种子中蜡酯含量下降了 60-70%，同时伴随着油质蛋白含量的减少和葡萄糖含量的增加。种子微粒体部分中荷荷巴脂酶的活性在萌发的前 50 天增加。这些酶对三酰基甘油的活性高于对蜡酯的活性。在 60 °C 和 pH 值约为 7 时观察到三酰基甘油和蜡酯的最大脂肪酶活性为 6.5-8。该酶有效地水解含有饱和和不饱和酰基和醇部分的各种蜡酯。我们还证明了当游离脂肪醇和不同的酰基供体（包括三酰基甘油和游离脂肪酸）用作底物时，荷荷巴脂酶具有蜡酯合成活性。对于酯化反应，酶使用饱和和不饱和脂肪醇，优先选择长链和超长链化合物。在体外试验中，荷荷巴脂酶在很宽的温度范围内催化三酰甘油和不同蜡酯的水解。此外，酶具有在逆反应中合成蜡酯的能力。我们的数据表明，霍霍巴脂酶可能比以前假设的更类似于其他植物脂酶。