Activity-based Probes for Gsp Amidase : tructure-guided Design, Synthesis and Evaluation.

Glutathionylspermidine (Gsp), an amide-bond conjugate of glutathione and spermidine, is mainly found in some protozoal parasites and E. coli. Glutathionylspermidine sythetase/amidase is a bifunctional enzyme with separate activity domains to catalyze both the synthesis and hydrolysis of Gsp. Recently we discovered that Gsp synthetase/amidase plays an important role in redox regulation in E. coli. The amidase activity changes depending on the condition of various oxidative stress. In order to qualitatively and quantitatively monitor the amidase activity level in vivo, it is necessary to design and synthesize specific activity-based probes (ABPs) to investigate how Gsp amidase is involved in redox regulation and how the synthetase and amidase communicate with each other in the oxidative defense. Based on the catalytic mechanism and X-ray structural information of Gsp amidase, the