Chuang R L, Chen J C, Chu J, Tzen J T
Graduate Institute of Agricultural Biotechnology, National Chung-Hsing University, Taiwan.
J Biochem. 1996 Jul;120(1):74-81. doi: 10.1093/oxfordjournals.jbchem.a021396.
Plant seeds store triacylglycerols in discrete organelles called oil bodies. An oil body stores a matrix of triacylglycerols surrounded by phospholipids and alkaline proteins termed oleosins. Oil bodies in rice seeds are present in embryos and aleurone layers. They do not coalesce in crowded environments, as observed on electron microscopy. The detected isoelectric point of purified rice oil bodies is pH 6.2. This implies that rice oil bodies possess a negatively charged surface at neutral pH. The suspension of rice oil bodies in pH 6.5 buffer induces aggregation. Presumably, the negatively charged surface causes electrostatic repulsion that maintains rice oil bodies as discrete organelles. Rice oil bodies lose their integrity on trypsin treatment. Undoubtedly, oleosins play an important role in the stability of oil bodies. There are two oleosin isoforms in rice oil bodies. Antibodies raised against these two homologous isoforms do not cross-recognize each other. Both isoforms are restricted to oil bodies, as detected on immuno-assaying. Partial amino acid sequences of these two isoforms were obtained, and compared with the deduced sequences of two maize and two rice oleosin genes. The comparison confirmed that the two major proteins in rice oil bodies are the two oleosin isoforms.
植物种子在称为油体的离散细胞器中储存三酰甘油。油体储存由磷脂和称为油质蛋白的碱性蛋白质包围的三酰甘油基质。水稻种子中的油体存在于胚和糊粉层中。如在电子显微镜下观察到的，它们在拥挤的环境中不会聚结。纯化的水稻油体检测到的等电点为pH 6.2。这意味着水稻油体在中性pH下具有带负电荷的表面。水稻油体在pH 6.5缓冲液中的悬浮液会诱导聚集。据推测，带负电荷的表面会引起静电排斥，从而使水稻油体保持为离散的细胞器。水稻油体在胰蛋白酶处理后失去其完整性。毫无疑问，油质蛋白在油体的稳定性中起重要作用。水稻油体中有两种油质蛋白同工型。针对这两种同源同工型产生的抗体不会相互交叉识别。如在免疫测定中检测到的，两种同工型都局限于油体。获得了这两种同工型的部分氨基酸序列，并与两个玉米和两个水稻油质蛋白基因的推导序列进行了比较。比较证实，水稻油体中的两种主要蛋白质是两种油质蛋白同工型。
