Stewart J M, Driedzic W R, Berkelaar J A
Department of Chemistry, Mount Allison University, New Brunswick, Canada.
Biochem J. 1991 May 1;275 ( Pt 3)(Pt 3):569-73. doi: 10.1042/bj2750569.
The proposed function of fatty-acid-binding proteins in facilitating the diffusion of their ligand has been examined in a cytosolic model using a steady-state diaphragm cell apparatus. The white muscle of ocean pout (Macrozoarces americanus) does not have a fatty-acid-binding protein: nor does it exhibit detectable beta-oxidative capacity, and as such is a good source of cytosol preparation. After determining the diffusion coefficient of oleate in this medium, fatty-acid-binding protein, isolated from the ventricle of this animal, was added and the apparent diffusion coefficient was again determined. The presence of the fatty-acid-binding protein increased the apparent diffusion coefficient of this long-chain fatty acid about 6-fold, from 0.087 x 10(-5) cm2.s-1 to 0.58 x 10(-5)cm2.s-1. This confirms the facilitated diffusion hypothesis as one role of fatty-acid-binding protein. The diffusion coefficients of oleate in 50 mM-sodium phosphate buffer, pH 7.4, at 10 degrees C and 25 degrees C (0.15 x 10(-5) cm2.s-1 and 0.28 x 10(-5) cm2.s-1 respectively) were also measured.
利用稳态隔膜池装置，在细胞溶质模型中研究了脂肪酸结合蛋白促进其配体扩散的假定功能。美洲绵鳚的白肌中没有脂肪酸结合蛋白，也没有可检测到的β-氧化能力，因此是制备细胞溶质的良好来源。在测定油酸在该介质中的扩散系数后，加入从该动物心室分离出的脂肪酸结合蛋白，并再次测定表观扩散系数。脂肪酸结合蛋白的存在使这种长链脂肪酸的表观扩散系数增加了约6倍，从0.087×10⁻⁵ cm²·s⁻¹增加到0.58×10⁻⁵ cm²·s⁻¹。这证实了促进扩散假说是脂肪酸结合蛋白的一个作用。还测量了油酸在pH 7.4的50 mM磷酸钠缓冲液中，10℃和25℃时的扩散系数（分别为0.15×10⁻⁵ cm²·s⁻¹和0.28×10⁻⁵ cm²·s⁻¹）。
