Carnitine acetyltransferase in nervous tissue.

Some of the kinetic properties of carnitine acetyltransferase in brain homogenates have been reported with the use of a new, sensitive radiometric method for the determination of acetylcarnitine. Those properties and the distribution pattern of carnitine acetyltransferase in various rat tissues, subcellular fractions, and discrete areas of the brain have been compared with those obtained for choline acetyltransferase and found to be markedly different. In subcellular fractions of brain, the carnitine enzyme remained associated with the mitochondrial fragments after “hypoosmotic” shock, whereas the choline enzyme showed enrichment in the “nerve ending particle” fraction. In developing brain cortex, the choline enzyme reaches adult levels of activity earlier than the camitine enzyme. Thus, we have concluded that the two enzymes appear to be associated with different morphological structures. Further, the uniform distribution of carnitine acetyltransferase within the nervous system, as well as its association with the mitochondrial fraction, argues against the hypothesis that acetylcarnitine functions in brain as a neurohumoral agent. These data support the concept that carnitine acetyltransferase is involved in the transport of acyl groups across mitochondrial membranes.