Summary
Pulse radiolysis and steady-state X-radiolysis have been used to investigate the radiation inactivation of aldolase from rabbit muscle. Both eaq− and OH readily react with aldolase, and contribute to inactivation. The radical anions (CNS)2− and (Br)2− react with aldolase at neutral pH. The progressive addition of alkali results in an increase in the second-order rate constants, with an apparent pK ∼ 10 ± 0·3, and with the formation of an unstable intermediate, λmax ∼400 nm resembling a phenoxyl radical. Steady-state radiolysis in the presence of (CNS)2− and (Br)2− at alkaline pH results in increased aldolase inactivation, with a pK of enzyme inactivation similar to that observed for reaction of the radical anions. We propose that a reaction of the radical anions with tyrosine residues accounts for the resultant inactivation.