Deuteration Kinetics of Tyrosine by Means of Fluorescence Measurement

When tyrosine was rapidly transferred from water into deuterium oxide medium by means of a stopped-flow device, a time-dependent change in the fluorescence intensity at 305 nm (excited at 275 nm) has been observed. The rate constant (ke) was found to be 116 s−1 at pH 5.8 and 14 °C. This ke value has been attributed to the rate constant of the O1H→O2H reaction of the phenolic OH group, on the basis of similar fluorescence examinations on phenol, anisole, glycyl-l-tyrosine, and Nα-acetyl-N-methyl-l-tyrosinamide as well as on the basis of a stopped-flow ultraviolet absorption study of tyrosine. The stopped-flow fluorometry has been applied to a study of tyrosine residues in yeast 3-phosphoglycerate kinase.