Pin1 is involved in eukaryotic cell proliferation by changing the structure and function of phosphorylated proteins. PiB, the Pin1 specific inhibitor, blocks cancer cell proliferation. However, low solubility of PiB in DMSO has limited studies of its effectiveness. We screened for additional Pin I inhibitors and identified the DMSO-soluble compound dipentamethylene thiuram monosulfide (DTM) that inhibits Pin1 activity with an EC50 Value of 4.1 mu M. Molecular modeling and enzyme kinetic analysis indicated that DTM competitively inhibits Pin1 activity, with a K-i value of 0.05 mu M. The K-D value of DTM with Pin1 was determined to be 0.06 mu M by SPR technology. Moreover, DTM specifically inhibited peptidyl-prolyl cis/trans isomerase activity in HeLa cells. FACS analysis showed that DTM induced G0 arrest of the HCT116 cells. Our results suggest that DTM has the potential to guide the development of novel antifungal and/or anticancer drugs. (C) 2009 Elsevier Inc. All rights reserved.