KINETIC-BEHAVIOR OF MUSCLE CARNITINE PALMITOYLTRANSFERASE-I IN THE LAMPREY GEOTRIA-AUSTRALIS, BEFORE AND AFTER THE MARINE TROPHIC PHASE

This study was aimed at determining whether the marked changes that oc cur in the diet during the life cycle of the lamprey Geotria australis , and thus also in the fatty acid composition of the triacylglycerol s tores, are accompanied by alterations in the v(max) and apparent K-0.5 of skeletal muscle carnitine palmitoyltransferase I (CPT I) towards t he CoA derivatives of the fatty acids 16:0, 16:1n-7, 18:1n-9, 18:2n-6, and 22:6n-3. The activity of CPT I towards the last four of these acy l CoAs increased progressively from the microphagous larvae to young a dults, prior to the onset of their marine trophic phase, to fully grow n adults, which had ceased feeding on fish and embarked on their spawn ing run. For example, the nu(max) of CPT I towards 18:1n-9 rose from 4 .4, to 7.6 to 11.5 nmol.min(-1).mg mitochondrial protein(-1) over the course of the three life-cycle stages. The values for the nu(max) of l amprey muscle CPT I towards the various CoA esters were not directly c orrelated with the percentage contributions of the corresponding fatty acids to the triacylglycerol stores. Despite very pronounced differen ces in the biochemistry, physiology, and physical activity of each lif e-cycle stage, as well as in the fatty acid composition of the triacyl glycerols, before and after the adult trophic phase, the nu(max) for C PT I was always greatest for 16:1n-7 and 18:1n-9. Because the reactivi ty of CPT I towards the latter two monoenoic fatty acids is also high in teleost fishes and in rat, such a characteristic may have been cons erved throughout vertebrate evolution. (C) 1998 Wiley-Liss, Inc.