Allylation and Alkylation of Biologically Relevant Nucleophiles by Diallyl Sulfides

Allyl sulfides are bioactive phytochemicals found in garlic, onion, and other members of the genus <i>Allium</i>. Here we showed that diallyl disulfide and diallyl trisulfide can transfer allyl side chains to low molecular weight thiols. Diallyl monosulfide is inert with respect to this allyl transfer reaction. On the other hand, diallyl sulfone, a known metabolite of diallyl monosulfide, alkylates both amines and thiols under physiologically relevant conditions via isomerization to an electrophilic vinyl sulfone

Reactions of 1,3-Diketones with a Dipeptide Isothiazolidin-3-one: Toward Agents That Covalently Capture Oxidized Protein Tyrosine Phosphatase 1B

Protein tyrosine phosphatase 1B (PTP1B) is a validated therapeutic target for the treatment of type 2 diabetes; however, the enzyme has been classified by some as an “undruggable target”. Here we describe studies directed toward the development of agents that covalently capture the sulfenyl amide “oxoform” of PTP1B generated during insulin signaling events. The sulfenyl amide residue found in oxidized PTP1B presents a unique electrophilic sulfur center that may be exploited in drug and probe design. Covalent capture of oxidized PTP1B could permanently disable the intracellular pool of enzyme involved in regulation of insulin signaling. Here, we employed a dipeptide model of oxidized PTP1B to investigate the nucleophilic capture of the sulfenyl amide residue by structurally diverse 1,3-diketones. All of the 1,3-diketones examined here reacted readily with the electrophilic sulfur center in the sulfenyl amide residue to generate stable covalent attachments. Several different types of products were observed, depending upon the substituents present on the 1,3-diketone. The results provide a chemical foundation for the development of agents that covalently capture the oxidized form of PTP1B generated in cells during insulin signaling events

Covalent Allosteric Inactivation of Protein Tyrosine Phosphatase 1B (PTP1B) by an Inhibitor–Electrophile Conjugate

Protein tyrosine phosphatase 1B (PTP1B) is a validated drug target, but it has proven difficult to develop medicinally useful, reversible inhibitors of this enzyme. Here we explored covalent strategies for the inactivation of PTP1B using a conjugate composed of an active site-directed 5-aryl-1,2,5-thiadiazolidin-3-one 1,1-dioxide inhibitor connected via a short linker to an electrophilic α-bromoacetamide moiety. Inhibitor–electrophile conjugate <b>5a</b> caused time-dependent loss of PTP1B activity consistent with a covalent inactivation mechanism. The inactivation occurred with a second-order rate constant of (1.7 ± 0.3) × 10² M^–1 min^–1. Mass spectrometric analysis of the inactivated enzyme indicated that the primary site of modification was C121, a residue distant from the active site. Previous work provided evidence that covalent modification of the allosteric residue C121 can cause inactivation of PTP1B [Hansen, S. K., Cancilla, M. T., Shiau, T. P., Kung, J., Chen, T., and Erlanson, D. A. (2005) <i>Biochemistry</i> <i>44</i>, 7704–7712]. Overall, our results are consistent with an unusual enzyme inactivation process in which noncovalent binding of the inhibitor–electrophile conjugate to the active site of PTP1B protects the nucleophilic catalytic C215 residue from covalent modification, thus allowing inactivation of the enzyme via selective modification of allosteric residue C121