Formic acid is a product of the alpha-oxidation of fatty acids by human skin fibroblasts: deficiency of formic acid production in peroxisome-deficient fibroblasts.

Human skin fibroblasts in culture can oxidize beta-methyl fatty acids, such as phytanic acid and 3-methylhexadecanoic acid, to CO2 and water-soluble products. The latter are released largely into the culture medium. The major water-soluble product formed from [1-14C]phytanic and [1-14C]3-methylhexadecanoic acids is [14C]formic acid. As phytanic acid and 3-methylhexadecanoic acids contain beta-methyl groups and theoretically cannot be degraded by beta-oxidation, we postulate that formic acid is formed from fatty acids by alpha-oxidation. The marked reduction in formic acid production from beta-methyl fatty acids in peroxisome-deficient skin fibroblasts suggests that peroxisomes are involved in the generation of C1 units.