Institute of Biology, University of Natural Sciences and Humanities, Prusa 12, 08-110 Siedlce, Poland.
Planta. 2013 Jun;237(6):1627-36. doi: 10.1007/s00425-013-1870-8. Epub 2013 Mar 29.
The last step in triacylglycerols (TAG) biosynthesis in oil seeds, the acylation of diacylglycerols (DAG), is catalysed by two types of enzymes: the acyl-CoA:diacylglycerol acyltransferase (DGAT) and phospholipid:diacylglycerol acyltransferase (PDAT). The relative contribution of these enzymes in the synthesis of TAG has not yet been defined in any plant tissue. In the presented work, microsomal preparations were obtained from sunflower and safflower seeds at different stages of development and used in DGAT and PDAT enzyme assays. The ratio between PDAT and DGAT activity differed dramatically between the two different species. DGAT activities were measured with two different acyl acceptors and assay methods using two different acyl-CoAs, and in all cases the ratio of PDAT to DGAT activity was significantly higher in safflower than sunflower. The sunflower DGAT, measured by both methods, showed significant higher activity with 18:2-CoA than with 18:1-CoA, whereas the opposite specificity was seen with the safflower enzyme. The specificities of PDAT on the other hand, were similar in both species with 18:2-phosphatidylcholine being a better acyl donor than 18:1-PC and with acyl groups at the sn-2 position utilised about fourfold the rate of the sn-1 position. No DAG:DAG transacylase activity could be detected in the microsomal preparations.
在油料种子中三酰基甘油(TAG)生物合成的最后一步，即二酰基甘油(DAG)的酰基化，由两种类型的酶催化：酰基辅酶 A：二酰基甘油酰基转移酶(DGAT)和磷脂：二酰基甘油酰基转移酶(PDAT)。这两种酶在任何植物组织中合成 TAG 的相对贡献尚未确定。在本研究中，从向日葵和红花种子的不同发育阶段获得微粒体制剂，并用于 DGAT 和 PDAT 酶测定。这两种不同物种之间 PDAT 和 DGAT 活性之间的比例差异很大。使用两种不同的酰基受体和两种不同的酰基辅酶 A 测定方法测量 DGAT 活性，在所有情况下，红花中 PDAT 与 DGAT 活性的比值均明显高于向日葵。用两种方法测量的向日葵 DGAT 对 18:2-CoA 的活性明显高于对 18:1-CoA，而红花酶则相反。另一方面，PDAT 的特异性在两种物种中相似，18:2-磷脂酰胆碱作为酰基供体优于 18:1-PC，并且 sn-2 位置的酰基利用率是 sn-1 位置的四倍左右。在微粒体制剂中未检测到 DAG：DAG 反式酰基转移酶活性。
