The Radiolysis of Glyceraldehyde-3-phosphate Dehydrogenase

Abstract

The yields in molecules per 100 eV for active-site and sulphydryl loss from glyceraldehyde-3-phosphate dehydrogenase have been determined in nitrousoxide-saturated, aerated and argon-saturated solutions. Molecular hydrogen peroxide produces a sulphenic acid product, which can be repaired by post-irradiation treatment with dithiothreitol. Comparison of the yields under various conditions showed that in aerated solutions both ·OH and ·O₂⁻ radicals inactivated the enzyme with an efficiency of about 26 per cent. However, the efficiency of ·OH in air-free solutions was less, and inactivation by ·H and e_aq⁻ did not appear to be appreciable. There is a correlation between SH loss and loss of active sites.