Thiopurine methyltransferase: structure-activity relationships for benzoic acid inhibitors and thiophenol substrates. 1986

M M Ames, and C D Selassie, and L C Woodson, and J A Van Loon, and C Hansch, and R M Weinshilboum

Twenty-seven substituted benzoic acids have been studied as inhibitors of partially purified human renal thiopurine methyltransferase (TPMT). Quantitative structure-activity relationship (QSAR) analysis resulted in the following equation: pI50 = 1.25( +/- 0.53)pi'3 + 0.73( +/- 0.38)MR3,4 + 2.92( +/- 0.39). In this equation pI50 is the -log of the concentration of compound that inhibits the enzyme activity by 50% (IC50);pi'3 is the relative hydrophobicity of the more hydrophobic of the two meta substituents; and MR3,4 is the molar refractivity of the more hydrophobic of the two meta substituents and of the para substituent on the phenyl ring. In addition, 14 substituted thiophenols were tested as substrates for the enzyme. All 14 thiophenols tested were excellent substrates with Km constants (0.8-7.8 microM) that were at least 2 orders of magnitude lower than those of any known thiopurine substrate for TPMT. However, there was no discernible relationship between the activities of thiophenol substrates and their physicochemical parameters. These results suggest that benzoic acid inhibitors of and thiophenol substrates for TPMT may interact with different sites on the enzyme.

UI MeSH Term Description Entries
D007668 Kidney Body organ that filters blood for the secretion of URINE and that regulates ion concentrations. Kidneys
D007700 Kinetics The rate dynamics in chemical or physical systems.
D008780 Methyltransferases A subclass of enzymes of the transferase class that catalyze the transfer of a methyl group from one compound to another. (Dorland, 28th ed) EC 2.1.1. Methyltransferase
D008956 Models, Chemical Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment. Chemical Models,Chemical Model,Model, Chemical
D010636 Phenols Benzene derivatives that include one or more hydroxyl groups attached to the ring structure.
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001565 Benzoates Derivatives of BENZOIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxybenzene structure. Benzoate,Benzoic Acids,Acids, Benzoic
D013329 Structure-Activity Relationship The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups. Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships
D013438 Sulfhydryl Compounds Compounds containing the -SH radical. Mercaptan,Mercapto Compounds,Sulfhydryl Compound,Thiol,Thiols,Mercaptans,Compound, Sulfhydryl,Compounds, Mercapto,Compounds, Sulfhydryl

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