Molecular species of fatty acid binding protein and their function in lipid metabolism

1.FABP的分子种类及其组织分布：从大鼠脑和心脏胞浆中提纯的FABP与L-FABP在免疫学上无关，在大鼠脑和心脏胞浆中均不存在L-FABP。因此，FABP分子物种的表达似乎是组织特异性的。免疫组织化学研究显示，阳性肝细胞在胎儿的腺泡内分布均匀，而在成人的门静脉周围分布均匀。结论：1.在大鼠肠上皮细胞分化过程中，L结合蛋白的表达发生了变化。电荷异构体的性质和FABP的功能：L-FABP的电荷异构体的起源部分是通过半胱氨酸在69位的共价修饰和结合脂肪酸的分子物种来解释的，油酸与L-FABP和H-FABP的结合没有差异。油酰DOA与H-FABP的结合是非饱和过程，可能是由于油酰CoA聚集体与H-FABP的非特异性结合所致。另一方面，油酰辅酶A与L-游离辅酶原具有特异性和可饱和性结合，每个分子只有一个结合部位。当以混合磷脂酰胆碱脂=某些形式加入脂肪酸时，L-辅酶原结合蛋白的活性增加，而H-游离辅酶原结合蛋白的活性没有增加。以脂肪酸-脂肪酸结合蛋白复合体为底物测定乙酰辅酶A合成酶活性时，发现H-脂肪酸结合蛋白对心脏细胞颗粒有选择性，L-脂肪酸结合蛋白对肝细胞颗粒有选择性。细胞反应：从猪脑胞浆中提纯了参与花生四烯酸释放的细胞反应的DG-激酶。免疫学研究表明，DG-激酶存在于脑的细胞质、微粒体和突触体膜中。脑组织免疫染色显示神经元呈阳性染色，而胶质细胞未见染色。尽管酶的磷酸化程度有限，但结果表明DG-K可以是一种磷化蛋白。

1. Molecular species of FABP and their tissue distribution:FABPs purified from rat brain and heart cytosol are immunologically unrelated to L-FABP and no L-FABP is present in either rat brain or heart cytosol. Thus, the ex= pression of FABP molecular species seems to be tissue specific. immunohistochemical studies revealed that the distribution pattern of the positive hepatocytes was uniform throughout the acini in fetuses but periportal in abults. In the rat intestine, the expression of L-FABP was changed in the course of ipithelial cell differentiation.2. Properties of charge isoforms and the function of FABPs:The origin of charge isoforms of L-FABP was partly explained by the covalent modi= fication of cysteine at 69 and by the molecular species of bound fatty acid.There are no difference in oleic acid binding to L-FABP and H-FABP. Binding of oleoyl DoA to H-FABP was nonsaturable process, possibly explained by nonspecific association of oleoyl CoA aggregates with H-FABP. On the other hand, there was specific and saturable binding of oleoyl CoA to L-FABP involving a single binding site per mole.Acly CoA synthetase activity of cell particulates was increased by the addition of L-FABP but not H-FABP, when fatty acid was added as the mixed phosphatidylcholine lipo= somes. The preference of H-FABP to heart cell particulates and L-FABP to liver cell particulates was demonstrated when acyl CoA synthetase activity was assayed using fatty acid-FABP complex as substrate.3. Cell response:DG-kinase which is involved in cell response of arachidonate release was purified from pig brain cytosol. Immunological studies show that DG-kinase is present in the cytosol as well as microsomal and synaptosomal membranes of the brain. Immunostaining of-brain tissues demonstrated that neurons were positively stained whereas glial cells were not stained. Although the extent of enzyme phosphorylation was limited, the results show that DG-kinase can be a phosphoprotein.