CARNITINE PALMITOYLTRANSFERASE ACTIVITY IS PRESENT AND HIGH IN THE MUSCLE AND LIVER OF LAMPREYS (AGNATHA)

The current study demonstrates for the first time that carnitine palmi toyltransferase (CPT), the rate-limiting enzyme of fatty acid oxidatio n in gnathostomatous (jawed) vertebrates, is present in the myotomal m usculature and liver of the adult migratory Southern Hemisphere lampre y Geotria australis, a representative of the agnathan (jawless) stage in vertebrate evolution. During the spawning run, the mean CPT capacit y at 20-degrees-C remained relatively constant in the muscle at 115 to 153 nmol/min.g, whereas in the liver it increased from a minimum of 1 62 nmol/min.g after four months of migration to 705 nmol/min.g at sexu al maturity. The maintenance of a substantial capacity for CPT activit y in the muscle, when the animal is relatively inactive during the mid dle phase of the run, would enable the animal to respond at such times to any environmental exigencies. It is proposed that the very high CP T capacity in the liver at sexual maturity is associated with an incre ased demand for ATP generation to facilitate the synthesis of glycogen that occurs in lampreys at this time. The trends shown by the activit y of cytochrome c oxidase in the liver and muscle parallel those of CP T, presumably reflecting the corresponding metabolic changes that are required by the animal. The results of the present and other studies i ndicate that the ability to store large amounts of lipid as triacylgly cerol, to bind and transport nonesterified fatty acids in the blood an d to utilise a CPT-dependent oxidative capacity in both the muscle and liver was present early in vertebrate evolution.