In most oilseeds, two evolutionarily unrelated acyl-CoA:diacylglycerol acyltransferase (DGAT) enzymes, DGAT1 and DGAT2, are the main contributors to the acylation of diacylglycerols in the synthesis of triacylglycerol. DGAT1 and DGAT2 are both present in the important crop oilseed rape (Brassica napus), with each type having four isoforms. We studied the activities of DGAT isoforms during seed development in microsomal fractions from two oilseed rape cultivars: edible, low-erucic acid (22:1) MONOLIT and nonedible high-erucic acid MAPLUS. Whereas the specific activities of DGATs were similar with most of the tested acyl-CoA substrates in both cultivars, MAPLUS had 6- to 14-fold higher activity with 22:1-CoA than did MONOLIT. Thus, DGAT isoforms with different acyl-CoA specificities are differentially active in the two cultivars. We characterized the acyl-CoA specificities of all DGAT isoforms in oilseed rape in the microsomal fractions of yeast cells heterologously expressing these enzymes. All four DGAT1 isoforms showed similar and broad acyl-CoA specificities. However, DGAT2 isoforms had much narrower acyl-CoA specificities: two DGAT2 isoforms were highly active with 22:1-CoA, while the ability of the other two isoforms to use this substrate was impaired. These findings elucidate the importance, which a DGAT isoform with suitable acyl-CoA specificity may have, when aiming for high content of a particular fatty acid in plant triacylglycerol reservoirs.

中文翻译：

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酰基辅酶A：二酰基甘油酰基转移酶2的同工型在本质上对芥酸的不同。

在大多数油料种子中，两种进化上不相关的酰基辅酶A：二酰基甘油酰基转移酶（DGAT）和DGAT1和DGAT2是三酰基甘油合成中二酰基甘油酰化的主要贡献者。DGAT1和DGAT2都存在于重要的农作物油菜（甘蓝型油菜）中，每种类型具有四个同工型。我们研究了来自两个油料油菜品种：可食用的低芥酸（22：1）MONOLIT和不可食用的高芥酸MAPLUS的微粒体级分中种子发育过程中DGAT同工型的活性。尽管两个品种中大多数测试的酰基辅酶A底物的DGAT的比活性相似，但MAPLUS的22：1-CoA活性比MONOLIT高6至14倍。因此，具有不同酰基辅酶A特异性的DGAT同工型在两个品种中具有不同的活性。我们在异源表达这些酶的酵母细胞的微粒体级分中表征了油菜中所有DGAT同工型的酰基辅酶A特异性。所有四个DGAT1亚型均显示出相似且广泛的酰基CoA特异性。但是，DGAT2同工型的酰基CoA特异性要窄得多：两种DGAT2同工型对22：1-CoA的活性很高，而其他两种同工型使用该底物的能力却受到了损害。这些发现阐明了以植物三酰甘油储库中特定脂肪酸的高含量为目标时，具有合适的酰基辅酶A特异性的DGAT同工型可能具有的重要性。但是，DGAT2同工型的酰基CoA特异性要窄得多：两种DGAT2同工型对22：1-CoA的活性很高，而其他两种同工型使用该底物的能力却受到了损害。这些发现阐明了以植物三酰甘油储库中特定脂肪酸的高含量为目标时，具有合适的酰基辅酶A特异性的DGAT同工型可能具有的重要性。但是，DGAT2同工型的酰基CoA特异性要窄得多：两种DGAT2同工型对22：1-CoA的活性很高，而其他两种同工型使用该底物的能力却受到了损害。这些发现阐明了以植物三酰甘油储库中特定脂肪酸的高含量为目标时，具有合适的酰基辅酶A特异性的DGAT同工型可能具有的重要性。