Thiol alkylating agents

Detwiler and co-workers were the first to demonstrate a role for csPDI in platelet physiology (Chen et al, 1995 Essex et al, 1995). Essex and co-workers (1999, 2001) and Hogg and co-workers (Burgess et al., 2000) showed that the inactivation of csPDI with anti-PDI antibodies and thiol alkylating agents inhibited platelet activation and aggregation. Recent studies have identified two distinct activities for csPDI. 

In addition to n-alanine and n-glutamate, many bacterial cell walls also contain meso-diaminopimelate (DAP) [2]. DAP is produced by epimerization from l,l-DAP to d,l-DAP by the cofactor independent diaminopimelate epimerase [97, 98]. The structure of this enzyme has been solved and two cysteines in the active site were proposed to be the acid-base catalysts [99]. The pattern of label incorporation from tritiated water is consistent with a two-base mechanism [97]. The enzyme has been shown to be stoichiometrically inhibited by the thiol alkylating agent aziDAP [97]. Interestingly, DAP epimerase has an equilibrium constant of 2 (Keq = [d,l]/[l,l]) duc to the statistically expected higher concentration of the [d,l] form at equilibrium between these species [100]. 

A similar approach has been used to prepare dithiocarbamates, xanlhates and unsymmetrical trithiocarbonates.478 Thus, unsymmetrical primary and secondary trithiocarbonates arc readily prepared in a one pot reaction by treating a thiol with carbon disulfide in the presence of triethylamine to form a carbotrilhioale salt and then adding the appropriate alkylating agent.457 47 The process is shown in Scheme 9.40 for 231.46j... 

This chapter reports on the reactivity of organic carbonates as alkylating agents, with emphasis on the lightest term of the series, DMC. Under both CF and batch conditions, DMC can react with a number of nucleophilic substrates such as phenols, primary amines, sulfones, thiols, and methylene-active derivatives of aryl and aroxy-acetic acids. The mechanistic and synthetic aspects of these processes will be elucidated. 

An alkylating agent (ICH2COO ) that acts as a potent irreversible inhibitor of enzymes containing reactive thiol, e-amino, and/or imidazole side-chain groups within their active sites. The carboxymethylation reaction with enzymes is typically a bimolecular process that takes place without rate-saturation behavior ... 

Acquired resistance to alkylating agents is a common event. Such resistance against the cytostatic activity can occur through at least three mechanisms. Increased thiol production can inactivate the agents. Also a decreased cell permeability to the drug can play a role. Increased capacity for DNA repair can mitigate cytotoxic activity. 

Possible biochemical mechanisms of resistance to alkylating agents include changes in ceU DNA repair capability, increases in cell thiol content (which in turn can serve as alternative and benign targets of alkylation), decreases in ceU permeability, and increased activity of glutathione transferases. Increased metaUothionein content has been associated with tumor cell resistance to cisplatin. 

Inhibitors of Thiol and Carboxyl Proteases. Thiol proteases are inactivated by peptide chloromethyl ketones (30) and other alkylating agents. Peptide diazomethyl ketones are much more selective reagents since they do not react with serine proteases as do chloromethyl ketones. Diazoketones have been applied to papain and cathepsin B (48) thus far and it appears that they should be applicable to most thiol proteases. Specificity should be obtainable by changing the peptide sequence of the inhibitor to match that of the enzyme being studied. 

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