Reactions of Radiation-induced I^·, I₂⁻ and I₃⁻ with Alcohol Dehydrogenase and Aldolase

Summary

Pulse-radiolysis experiments are described on the reactions occurring between the enzymes, yeast alcohol dehydrogenase (ADH) and rabbit muscle adolase (ALD), and radiation-induced transient species arising from the iodide ion (I⁻) Rate-constants for the reactions of iodine atoms (I^·) and the radical ion (I⁻₂) with the two enzymes are reported, and some transient spectra are presented. Attempts to separate the reactions of the various species are described, and evidence given that ALD is, in general, less reactive than ADH with the transient species. The results clearly indicate that reactions of the enzymes with I₂⁻ are of greatest significance; reactions with I^· are of less importance, and I₃⁻ reactions only occur after the initial processes are completed. The role of these processes and the part played by the enzyme −SH groups in the radiation sensitivity of the enzymes is discussed.