Generation of volatile hydrocarbons from amino acids and proteins by an iron/ascorbate/GSH system

Incubation of free, but not of peptide-bound methionine in an iron/ascorbate system resulted in ethylene generation, which was inhibited by glutathione. Leucine and isoleucine, however, when incubated in an iron/ascorbate/GSH system, released small amounts of propane and ethane, respectively. Peptide-bound leucine additionally yielded butane, as did bovine serum albumin or casein. Hydrocarbon generation from amino acids was inhibited by hydroxyl radical scavengers, but catalase and superoxide dismutase were more efficient. Additionally, ethane and propane generation in this system was optimal at pH 6.2 suggesting the involvement of protonated superoxide besides OH-radicals which attack the side chains of Leu and Ile and very probably produce carbon-centered radicals, which should abstract a hydrogen atom from the thiol group of GSH resulting in the formation of saturated hydrocarbons.