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[摘要]：The mechanism of the cell cycle regulatory peptidyl prolyl isomerase (PPIase), Pin1, was investigated using reduced-amide inhibitors designed to mimic the twisted-amide transition state. Inhibitors, R-pSer-Psi[CH(2)N]-Pro-2-(indol-3-yl)ethylarnine, 1 [R = fluorenylmethoxycarbonyl (Fmoc)] and 2 (R = Ac), of Pin1 were synthesized and bioassayed. Inhibitor 1 had an IC(50) value of 6.3 mu M, which is 4.5-fold better for Pin1 than our comparable ground-state analogue, a cis-amide alkene isostere-containing inhibitor. The change of Fmoc to Ac in 2 improved aqueous solubility for structural determination and resulted in an IC(50) value of 12 mu M. The X-ray structure of the complex of 2 bound to Pin1 was determined to 1.76 angstrom resolution. The structure revealed that the reduced amide adopted a conformation similar to the proposed twisted-amide transition state of Pin 1, with a trans-pyrrolidine conformation of the prolyl ring. A similar conformation of substrate would be destabilized relative to the planar amide conformation. Three additional reduced amides, with Thr replacing Ser and L- or D-pipecolate (Pip) replacing Pro, were slightly weaker inhibitors of Pin1. |
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