Journal of Lipid Research, Vol. 43, 646-653, April 2002
Copyright © 2002 by Lipid Research, Inc.
Very long chain n-3 and n-6 polyunsaturated fatty acids bind strongly to liver fatty acid-binding protein
Andrew W. Norrisa and
Arthur A. Spectorb
a Department of Pediatrics, University of Iowa College of Medicine, Iowa City, IA 52242
b Department of Biochemistry, University of Iowa College of Medicine, Iowa City, IA 52242
Correspondence to:
Andrew W. Norris, at Joslin Diabetes Center, Cellular and Molecular Physiology, One Joslin Place, Boston, MA 02215., andrew.norris{at}joslin.harvard.edu (E-mail)
Synthesis of n-3 and n-6 very long chain-PUFAs (VLC-PUFAs) from 18-carbon essential fatty acids is differentially regulated. The predominant product arising from n-3 fatty acids is docosahexaenoic acid (22:6n-3), with the liver serving as the main site of production. The synthetic pathway requires movement of a 24-carbon intermediate from the endoplasmic reticulum to peroxisomes for retroconversion to 22:6n-3. The mechanism of this intra-organelle flux is unknown, but could be binding-protein facilitated. We thus investigated binding of a series of previously untested VLC-PUFAs to liver fatty acid-binding protein (L-FABP). Three fluorometric assays were employed, all of which showed strong binding (Kd'
10-8 to 10-7 M) of 20-, 22-, and 24-carbon n-3 PUFAs to L-FABP. In contrast, synthesis of the predominant n-6 PUFA product, arachidonic acid, does not require intra-organelle transport. However, we found that n-6 VLC-PUFAs bound to L-FABP with affinities (Kd'
10-8 to 10-7 M) comparable to their n-3 counterparts.
Although these results raise the possibility that L-FABP may participate in the cytoplasmic processing of n-3 and n-6 VLC-PUFAs, there is no evidence on the basis of binding affinities that L-FABP accounts for differences in the predominant products formed by the n-3 and n-6 PUFA metabolic pathways.Norris, A. W., and A. A. Spector. Very long chain n-3 and n-6 polyunsaturated fatty acids bind strongly to liver fatty acid-binding protein. J. Lipid Res. 2002. 43: 646653.
Supplementary key words:
24-carbon polyunsaturated fatty acids, docosahexaenoic acid, arachidonic acid, fatty acid binding assay