Safford R, Moran M T, De Silva J, Robinson S J, Moscow S, Jarman C D, Slabas A R
Dept of Biological Sciences, University of Durham, UK.
Transgenic Res. 1993 Jul;2(4):191-8. doi: 10.1007/BF01977349.
Medium chain hydrolase (MCH) is an enzyme which regulates the chain length of fatty acid synthesis specifically in the mammary gland of the rat. During lactation, MCH interacts with fatty acid synthase (FAS) to cause premature release of acyl chains, thus providing medium chain fatty acids for synthesis of milk fat. In this study we have investigated the ability of rat MCH to interact with the phylogenetically more distant FAS structure present in plant systems and to cause a perturbation of fatty acid synthesis. In in vitro experiments, addition of purified MCH to rapeseed homogenates was found to cause a significant perturbation of fatty acid synthesis towards medium chain length products. The rat MCH gene was expressed in transgenic oilseed rape using a seed specific rape acyl carrier protein (ACP) promoter and a rape ACP plastid targeting sequence. Western analysis showed MCH protein to be present in transgenic seed and for its expression to be developmentally regulated in concert with storage lipid synthesis. The chimaeric preprotein was correctly processed and immunogold labelling studies confirmed MCH to be localized within plastid organelles. However, fatty acid analysis of oil from MCH-expressing rape seed showed no significant differences to that from control seed.
中链水解酶（MCH）是一种专门在大鼠乳腺中调节脂肪酸合成链长的酶。在哺乳期，MCH与脂肪酸合酶（FAS）相互作用，导致酰基链过早释放，从而为乳脂肪的合成提供中链脂肪酸。在本研究中，我们研究了大鼠MCH与植物系统中系统发育上距离更远的FAS结构相互作用以及引起脂肪酸合成紊乱的能力。在体外实验中，发现向油菜籽匀浆中添加纯化的MCH会导致脂肪酸合成朝着中链长度产物发生显著紊乱。使用种子特异性油菜酰基载体蛋白（ACP）启动子和油菜ACP质体靶向序列，将大鼠MCH基因在转基因油菜籽中进行表达。蛋白质免疫印迹分析表明，MCH蛋白存在于转基因种子中，并且其表达与储存脂质合成协同受到发育调控。嵌合前体蛋白被正确加工，免疫金标记研究证实MCH定位于质体细胞器内。然而，对表达MCH的油菜籽油脂的脂肪酸分析表明，与对照种子的油脂没有显著差异。
