INFLUENCE OF DIET ON THE KINETIC-BEHAVIOR OF HEPATIC CARNITINE PALMITOYLTRANSFERASE-I TOWARD DIFFERENT ACYL COA ESTERS

The influence of diet on the kinetics of the overt form of rat liver m itochondrial carnitine palmitoyltransferase (CPT I; EC 2.3.1.21) was s tudied using rats fed either a low-fat diet (3% w/w fat), or diets whi ch were supplemented with either olive oil (OO), safflower oil (SO) or menhaden (fish) oil (MO) to 20% w/w of fat (high fat diets). When ani mals were fed each of these four diets for 10 days, the order of the a pparent maximal activity (v(max)) of CPT I toward various individual f atty acyl CoA, when measured under a fixed molar ratio of acyl CoA/alb umin, was 16:1n-7>18:1n-9>18:2n-6>16:0>22:6n-3, and was thus not affec ted by the fat composition of the diet. However, in all for but one ca se, the SO and MO diets elicited a higher v(max) each substrate than e ither the LF diet or the high fat OO diet. The apparent K-0.5 for the different acyl CoA esters was generally lowest in LF-fed animals, and highest in those fed the high-fat SO diet. Moreover, when compared wit h the situation of animals fed high-fat diets, the K-0.5 Values of CPT I in LF-fed animals for palmitoyl CoA and oleoyl CoA were low. This p ossession by CPT I of a high ''affinity'' toward these nonessential fa tty acyl CoAs, but a lower ''affinity'' toward linoleoyl CoA, the este r of an essential fatty acid, may enable this latter fatty acid to be spared from oxidation when its concentration in the diet is low. The d ata also emphasize that palmitoleoyl CoA, if available in the diet, is likely to be utilized by CPT I at a high rate.