In conclusion, several facts should

In conclusion, several facts should be stressed. To our knowledge, until this moment (June 2012), three different mechanisms have been proposed and partially documented for the degradation of compounds having a quaternary car-bon atom in the molecule (see Fig. 3, which shows only the key steps of individual proposed mechanisms). The first involves hydroxylation of a methyl group to give diol; the second, a rearrangement of carboxyl by pivalyl-CoA mu-tase, and the third, a “rearrangement” of methyl group yielding a metabolite with tertiary carbon.One of the possibilities of answering the question, whether pivalic acid is anthropogenic, can be the use of a combination of experiments published so far. As mentioned above, the enzymes GkIcmF and CmIcmF (Cracan and Banerjee 2012) can transform isovaleryl-CoA to pivalyl-CoA by 1,2-rear-rangement. By using commercially available Leu isotopicallylabeled either by deuterium (L-leucine-5,5,5-D3, L-leucine-D10, and L-leucine-isopropyl-D7) or by 13C (L-leucine-3-13Cor L-leucine-13C6) or their combination (L-leucine-13C6,D10) or isovaleric acid (α-ketoisovaleric acid-U-13C5,3-D1 or α-ketoisovaleric acid-U-13C5), the enzyme reactions can be assumed to yield labeled pivalyl-CoA.