The incorporation of oxygen-18 into oxindole acid by cells of Hygrophorous conicus

To understand the mechanism of a biological oxidation in which oxygen is incorporated into a substrate, it is necessary to determine the origin of the incorporated oxygen. The objective of this investigation was to determine the origin of the oxygen atom incorporated into indoleacetic acid (IAA) by the IAA oxidase of Hygrophorous conicus through the use of oxygen-18. To determine the source of the oxygen atom incorporated into IAA it is necessary to incubate H. conicus cells with tryptamine or IAA in the presence of ¹⁸O₂ and H₂¹⁶O in one case and ¹⁶O₂ and H₂¹⁸O in another. An examination of H. conicus cells incubated with tryptamine led to the conclusion that an oxygen-18 atmosphere would be difficult to maintain for periods required to obtain isolatable amounts of OIAA. The ¹⁸O₂ and H₂¹⁶O experiment was not conducted. Isolated ¹⁶O₂ and H₂¹⁸O experiments was pyrolyzed. The CO₂ so obtained was analyzed on the mass spectrometer for percent enrichment. The results obtained indicate the oxygen atom incorporated into IAA by the IAA oxidase of H. conicus is not done so from water by a hydration-dehydrogenation reaction. IAA oxidase of H. conicus is probably a mono-oxygenase and the incorporated oxygen atom is derived from atmospheric oxygen--Abstract, Page i