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：从大鼠脑和心脏细胞质中纯化的FABP与L-FABP免疫无关，在大鼠脑和心脏细胞质中均不存在L-FABP。因此，FABP分子种的表达似乎具有组织特异性。免疫组织化学研究显示，阳性肝细胞在胎儿的整个腺泡中分布均匀，而在成人的门脉周围分布均匀。在大鼠肠上皮细胞分化过程中，L-FABP的表达发生变化。带电荷异构体的性质和功能：L-FABP带电荷异构体的起源部分可以用半胱氨酸69位点的共价修饰和结合脂肪酸的分子种类来解释。油酸与L-FABP和H-FABP的结合没有差异。油酰基DoA与H-FABP的结合是一个不饱和的过程，可能是由于油酰基CoA聚集体与H-FABP的非特异性结合。另一方面，油基CoA与L-FABP具有特异性和饱和的结合，每摩尔只有一个结合位点。当混合磷脂酰胆碱脂体中添加脂肪酸时，添加L-FABP可提高细胞颗粒的Acly CoA合成酶活性，但不增加H-FABP的活性。以脂肪酸- fabp复合物为底物测定酰基辅酶a合成酶活性时，证实了H-FABP对心脏细胞颗粒和L-FABP对肝细胞颗粒的偏好。细胞反应：从猪脑细胞质中纯化了参与花生四烯酸酯释放细胞反应的dg激酶。免疫学研究表明，dg激酶存在于脑的细胞质以及微粒体和突触体膜中。脑组织免疫染色显示神经元阳性，而胶质细胞未染色。虽然酶的磷酸化程度有限，但结果表明dg -激酶可以是一种磷酸化蛋白。

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.