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脂肪酸结合蛋白:对微粒体磷脂酸形成的刺激作用。

Fatty acid binding protein: stimulation of microsomal phosphatidic acid formation.

作者信息

Jolly C A, Hubbell T, Behnke W D, Schroeder F

机构信息

Department of Physiology and Pharmacology, Texas A & M University 77843-4466, USA.

出版信息

Arch Biochem Biophys. 1997 May 1;341(1):112-21. doi: 10.1006/abbi.1997.9957.

Abstract

The effect of fatty acid binding proteins (FABPs) on two key steps of microsomal phosphatidic acid formation was examined. Rat liver microsomes were purified by size-exclusion chromatography to remove endogenous cytosolic fatty acid and fatty acyl-CoA binding proteins while recombinant FABPs were used to avoid cross-contamination with such proteins from native tissue. Neither rat liver (L-FABP) nor rat intestinal fatty acid binding protein (I-FABP) stimulated liver microsomal fatty acyl-CoA synthase. In contrast, L-FABP and I-FABP enhanced microsomal conversion of [14C]oleoyl-CoA and glycerol 3-phosphate to [14C]phosphatidic acid by 18- and 7-fold, respectively. The mechanism for this stimulation, especially by I-FABP, is not known. However, several observations presented here suggest that, like L-FABP, I-FABP may interact with fatty acyl-CoA and thereby stimulate enzyme activity. First, I-FABP decreased microsomal membrane-bound oleoyl-CoA. Second, oleoyl-CoA displaced I-FABP bound fluorescent fatty acid, cis-parinaric acid, with Ki of 5.3 microM and 1.1 sites. Third, oleoyl-CoA decreased I-FABP tryptophan fluorescence with a Kd of 4.2 microM. Fourth, oleoyl-CoA red shifted emission spectra of acrylodated I-FABP, a sensitive marker of I-FABP interactions with ligands. In summary, the results demonstrate for the first time that both L-FABP and I-FABP stimulate liver microsomal phosphatidic acid formation by enhancing synthesis of phosphatidate from fatty acyl-CoA and glycerol 3-phosphate.

摘要

研究了脂肪酸结合蛋白(FABP)对微粒体磷脂酸形成两个关键步骤的影响。通过尺寸排阻色谱法纯化大鼠肝脏微粒体,以去除内源性胞质脂肪酸和脂肪酸酰基辅酶A结合蛋白,同时使用重组FABP以避免与天然组织中的此类蛋白发生交叉污染。大鼠肝脏脂肪酸结合蛋白(L-FABP)和大鼠肠道脂肪酸结合蛋白(I-FABP)均未刺激肝脏微粒体脂肪酸酰基辅酶A合酶。相反,L-FABP和I-FABP分别将[14C]油酰辅酶A和甘油3-磷酸向[14C]磷脂酸的微粒体转化率提高了18倍和7倍。这种刺激的机制,尤其是I-FABP的刺激机制尚不清楚。然而,本文提出的几项观察结果表明,与L-FABP一样,I-FABP可能与脂肪酸酰基辅酶A相互作用,从而刺激酶活性。首先,I-FABP降低了微粒体膜结合的油酰辅酶A。其次,油酰辅酶A取代了与I-FABP结合的荧光脂肪酸顺式-十八碳四烯酸,其解离常数(Ki)为5.3微摩尔,结合位点为1.1个。第三,油酰辅酶A降低了I-FABP色氨酸荧光,解离常数(Kd)为4.2微摩尔。第四,油酰辅酶A使丙烯酰化I-FABP的发射光谱发生红移,这是I-FABP与配体相互作用的敏感标记。总之,结果首次证明L-FABP和I-FABP均通过增强脂肪酸酰基辅酶A和甘油3-磷酸合成磷脂酸来刺激肝脏微粒体磷脂酸的形成。

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