Figure 2 shows the amino acid seque

Figure 2 shows the amino acid sequences of selected parts of mutases from different bacteria. They show considerable similarity; to our mind, it is just a matter of time when some bacteria, probably those living in extreme habitats, will be found to possess a mutase with high activity to isovaleryl-CoA, which is similar to the activity of isobutyryl-CoA or methylmalonyl-CoA mutases to isobutyryl- or methylmalonyl-CoA, respectively.The incorporation of short-chain branched fatty acids (FAs) as starter units was first published in 1971 (Willecke and Pardee 1971). A mutant strain of Bacillus subtilis de-fective in branched chain α-keto acid dehydrogenase was used to incorporate, among others, pivalic acid into fatty acids. Addition of pivalic acid into the medium yielded two homologues, i.e., 12,12-dimethyltridecanoic and 14,14-dimethylpentadecanoic acids in amounts of 13 and 24 % of total FAs, respectively. These data confirmed that even a highly branched acid, such as pivalic acid, can serve as a starter unit in the biosynthesis of FA.