The Localization and Function of Carnitine Acetyltransferase in the Flight Muscles of the Locust

In order to determine the extent to which carnitine acetyltransferase is restricted to mitochondria, its occurrence in fractions of the flight muscles of Locusta migratoria , obtained by two different procedures, was checked by simultaneous assay of known mitochondrial enzymes. In one procedure, fractionated extraction of the muscles was achieved by gently stirring the tissue successively in isotonic sucrose and phosphate buffer after which the residue was disrupted in phosphate buffer. In the second procedure fractionation was achieved by differential centrifugation. In both procedures the partitioning of the carnitine acetyltransferase among all fractions closely paralleled that of the intramitochondrial marker enzymes, thus strongly suggesting that carnitine acetyltransferase is exclusively localized within mitochondria–possibly with the transferase occurring in two intramitochondrial compartments separated from each other by a mimbrane which is impermeable to acetyl CoA. The last‐named hypothesis is furthermore supported by correlated studies on mitochondrial respiration using acetate derivatives as substrates.