Ethylene biosynthesis: 3. Evidence concerning the fate of C1-N1 of 1-aminocyclopropane carboxylic acid

Evidence has been obtained that the product of ethylene biosynthesis from 1-aminocyclopropane carboxylic acid (ACC), aside from CO₂, is cyanide. This has been accomplished by synthesis of a carbon-13-labeled ACC, feeding to apple tissue, and isolation of the free amino acids. By enzymatic degradation to CO₂, followed by mass spectrometry, label is shown to be incorporated into the 4-carbon of asparagine. This occurs via well-known pathways for the metabolism of cyanide, and is confirmed by incorporation experiments using labeled cyanide. In conjunction with previous stereochemical studies, evidence for a sequential single-electron transfer pathway for ethylene biosynthesis has been considerably strengthened.