IN VITRO FATTY ACID OXIDATION BY DEVELOPING TISSUES IN ADULT OF BLOWFLY, LUCILIA

Homogenates of abdomens and thoraces of the blowfly, Lucilia cuprina, oxidized butyrate with maximal rates at adult emergence. The oxidation of butyrate by a particulate preparation from thoraces of newly emerged Lucilia required malate (0·5 mM) and was stimulated by ATP (2 mM). The rates of O2 uptake, corrected for the endogenous respiration which itself appeared to be due to fatty acid oxidation, were 20-30 μl of O2/mg mitochondrial protein per hr. CoA, carnitine, and bovine plasma albumin did not increase the O2 uptake but DNP inhibited respiration in the presence of ATP; this inhibition was reversed by oligomycin. Butyrylcarnitine was not oxidized more rapidly than butyrate. Palmitate oxidation was stimulated by bovine plasma albumin, malate, ATP, CoA, and carnitine and inhibited by DNP. The O2 uptake with palmitylcarnitine was considerably greater (80 μl of O2/mg mitochondrial protein per hr) than with any system in which palmitate itself was the substrate (10-15 μl/mg mitochondrial protein per hr). ATP (0·5 mM) was required for maximal rates of oxidation of palmitylcarnitine but not of butyrylcarnitine. The distribution of enzyme activity during density gradient centrifugation indicated that the developing sarcosomes themselves are responsible for the oxidation. © 1969.