Studies on the Fatty Acid Binding Proteins in Cytosol of Rat Liver

Abstract

Gel filtration on Sephadex G-75 of crude rat liver supernatant preincubated with [1-14C]oleic acid yields three peaks of radioactivity which are attributed to the presence in these fractions of fatty acid binding proteins. We have confirmed these observations with binding assays by phase partition, polyacrylamide gel electrophoresis, and thin layer electrofocusing. Peak I (mol. wt. 60,000 pI 5.01 was shown to be albumin, which mainly arises from a contamination of the liver preparation by blood. Peak II (mol. wt. 10,000, pI 5.9) is a fatty acid binding protein. Finally peak III (mol. wt. 1500, pI 5.7) is a fatty acid binding component, the chemical nature of which was not elucidated. These fatty acid binding fractions have no effect on the reaction of acyl-CoA synthetase whereas the crude liver supernatant does stimulate the activation of fatty acid as shown earlier. In consequence, the physiological role of these fatty acid binding fractions is not yet elucidated.

Stimulation of triacylglycerol synthesis by Z protein in rat liver and intestinal mucosa

“…Suzue and Marcel [20] have recently reported the isolation of a new fatty acid binding protein from the cytosol of rat liver and have made a preliminary examination of its effect upon the acylation of 1 -palmitoyl lyso phosphatidylcholine by rat liver microsomes. No stimulation could be demonstrated for the new cytosolic protein or albumin and the Z protein which were clearly resolved from it.…”

“…In an earlier study, Manley et al [8] showed that triacylglycerol synthesis in rat liver microsomes can be stimulated by the addition of cytosol and suggested that the cytosol may contain one or more proteins which operate as carriers of acyl CoAs in the synthesis of triacylglycerols. Suzue and Marcel [20] have recently reported the isolation of a new fatty acid binding protein from the cytosol of rat liver and have made a preliminary examination of its effect upon the acylation of 1 -palmitoyl lyso phosphatidylcholine by rat liver microsomes. No stimulation could be demonstrated for the new cytosolic protein or albumin and the Z protein which were clearly resolved from it.…”

Tissue phospholipid fatty acid composition in genetically lean (Fa/−) or obese (fa/fa) zucker female rats on the same diet

“…The conversion process involves liver microsomal desaturases (4,5) and, in particular, two enzymes whose activity, in a defmed nutritional context, determines the quantity of long-chain PUFA available to the organism: (i) A6-desaturase that permits the conversion of 18:2n-6 to ~/-linolenic acid (18:3n-6) and the conversion of 18:3n-3 to stearidonic acid (18:4n-3); this enzyme is generally considered the rate limiting step in PUFA desaturation (6)(7)(8); and (ii) A5-desaturase that permits the conver-*To whom correspondence should be addressed. Abbreviations: BHT, butylhydroxytoluene; GLC, gas-liquid chromatography; FFAP, free fatty acid phase; MUFA, monounsaturated fatty acids; PL, phospholipids; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids; TSL, total serum lipids.…”

Concomitant increase in hepatic triacylglycerol biosynthesis and cytosolic fatty-acid-binding-protein content after feeding rats with a cholestyramine-containing diet

“…Interestingly the small fatty-acid-binding fraction of Mr 1500-2000 of the cytosol-of control rats (Fig. 3), which contains a fatty-acid-binding peptide (Suzue & Marcel, 1975;Rustow et al, 1979), was absent from the cytosol of cholestyramine-fed rats.…”