Carnitine palmitoyltransferase activity is present and high in the muscle and liver of lampreys (Agnatha)

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Abstract
The current study demonstrates for the first time that carnitine palmitoyltransferase (CPT), the rate‐limiting enzyme of fatty acid oxidation in gnathostomatous (jawed) vertebrates, is present in the myotomal musculature and liver of the adult migratory Southern Hemisphere lamprey Geotria australis, a representative of the agnathan (jawless) stage in vertebrate evolution. During the spawning run, the mean CPT capacity at 20°C remained relatively constant in the muscle at 115 to 153 nmol/min.g, whereas in the liver it increased from a minimum of 162 nmol/min.g after four months of migration to 705 nmol/min.g at sexual maturity. The maintenance of a substantial capacity for CPT activity in the muscle, when the animal is relatively inactive during the middle phase of the run, would enable the animal to respond at such times to any environmental exigencies. It is proposed that the very high CPT capacity in the liver at sexual maturity is associated with an increased demand for ATP generation to facilitate the synthesis of glycogen that occurs in lampreys at this time. The trends shown by the activity of cytochrome c oxidase in the liver and muscle parallel those of CPT, presumably reflecting the corresponding metabolic changes that are required by the animal. The results of the present and other studies indicate that the ability to store large amounts of lipid as triacylglycerol, to bind and transport nonesterified fatty acids in the blood and to utilise a CPT‐dependent oxidative capacity in both the muscle and liver was present early in vertebrate evolution.