Modification of creatine kinase by S-nitrosothiols: S-nitrosation vs. S-thiolation

Creatine kinase is reversibly inhibited by incubation with S-nitrosothiols. Loss of enzyme activity is associated with the depletion of 5,5'-dithiobis (2-nitrobenzoic acid)-accessible thiol groups, and is not due to nitric ox ide release from RSNO. Full enzymatic activity and protein thiol content ar e restored by incubation of the S-nitrosothiol-modified protein with glutat hione. S-niuoso-N-acetylpenicillamine, which contains a more sterically hin dered S-nitroso group than S-nitrosoglutathione, predominantly modifies the protein thiol to an S-nitrosothiol via a transnitrosation reaction. In con trast, S-nitrosoglutathione modifies creatine kinase predominantly by S-thi olation. Both S-nitroso-N-acetylpenicillamine and S-nitrosoglutathione modi fy bovine serum albumin to an S-nitroso derivative. This indicates that S-t hiolation and S-nitrosation are both relevant reactions for S-nitrosothiols , and the relative importance of these reactions in biological systems depe nds on both the environment of the protein thiol and on the chemical nature of the S-nitrosothiol. (C) 2000 Elsevier Science Inc.