The Mode of Oxidation of Certain Fatty Acids with Branched Chains.

Our knowledge of the mechanism by which the simpler fatty acids with branched chains are oxidised in the body is still very meagre. This is no doubt due to the difficulty in interpreting the experimental results so far obtained, in any way that will lead to a generalisation such as we possess for the normal fatty acids; namely, f-oxidation followed by removal of the two end carbon atoms of the acid. This difficulty may be illustrated by reference to the behaviour of a-methvlbutyric acid and a-ethylbutyric acid. In the diabetic organism the former gives rise to increased " acetone body " production [Baer and Blum, 1906] whereas the latter yields, in part at any rate, methyl propyl ketone [Blum and Koppel, 1911]. Similarly a-methylpropionic acid (isobutyric acid), gives rise to extra glucose formation [Ringer, Frankel and Jonas, 1913] and traces of d-lactic acid [Baer and Blum, 1906], a result interpreted by Baer and Blum as indicating that lactic acid is a probable intermediate stage in the oxidation of isobutyric acid, the methyl group being replaced by a hydroxyl group, thus: