Catabolism of 2-methyloctanoic acid and 3beta-hydroxycholest-5-en-26-oic acid.

1. 2-Methyl[1-(14)C]octanoic acid was synthesized from 2-bromo-octane and (14)CO(2). 2. 2-Methyl[1-(14)C]octanoic acid was readily oxidized to propionic acid and carbon dioxide by mitochondrial preparations from liver, less readily oxidized by adrenal and kidney (mitochondria), and only poorly oxidized by heart, spleen and brown fat (mitochondria). 3. 3beta-Hydroxy[26-(14)C]cholest-5-en-26-oic acid was rapidly oxidized by mammalian-liver mitochondria to propionic acid and carbon dioxide. Caiman-liver and toad-liver mitochondria also oxidized this steroid acid. 4. The oxidation of propionic acid, octanoic acid and palmitic acid by mitochondrial preparations from these various tissues was also studied. 5. Added carnitine did not stimulate 2-methyloctanoic acid oxidation and feebly stimulated 3beta-hydroxycholest-5-en-26-oic acid oxidation. 6. The significance of these results is discussed in relation to sterol catabolism in mammals and non-mammalian species.