In vitro reactivity of carboxylic acid-CoA thioesters with glutathione.
The chemical reactivity of acyl-CoA thioesters toward nucleophiles has been demonstrated in several recent studies. Thus, intracellularly formed acyl-CoAs of xenobiotic carboxylic acids may react covalently with endogenous proteins and potentially lead to adverse effects. The purpose of this study was to investigate whether a correlation could be found between the structure of acyl-CoA thioesters and their reactivities toward the tripeptide, glutathione (gamma-Glu-Cys-Gly). The acyl-CoA thioesters of eight carboxylic acids (ibuprofen, clofibric acid, indomethacin, fenbufen, tolmetin, salicylic acid, 2-phenoxypropionic acid, and (4-chloro-2-methyl-phenoxy)acetic acid (MCPA)) were synthesized, and each acyl-CoA (0.5 mM) was incubated with glutathione (5.0 mM) in 0.1 M potassium phosphate (pH 7.4, 37 degrees C). All of the acyl-CoAs reacted with glutathione to form the respective acyl-S-glutathione products, with MCPA-CoA having the highest rate of conjugate formation (120 +/- 10 microM/min) and ibuprofen-CoA having the lowest (1.0 +/- 0.1 microM/min). The relative reactivities of the acyl-CoAs were dependent on the substitution at the carbon atom alpha to the acyl carbon and on the presence of an oxygen atom in a position beta to the acyl carbon and were as follows: phenoxyacetic acid > o-hydroxybenzoic acid--phenoxypropionic acid > arylacetic acid derivatives > 2-methyl-2-phenoxypropionic acid--2-phenylpropionic acid. For each acyl-CoA thioester, the overall hydrolysis rate was determined as the time-dependent formation of parent compound. A linear trend was observed when comparing the reactivities of the acyl-CoAs with glutathione with the corresponding overall hydrolysis rates. Thus, the most reactive compound (MCPA-CoA) was also the compound with the highest rate of hydrolysis and the least reactive compounds (ibuprofen-CoA, clofibryl-CoA) were also the compounds least susceptible to hydrolysis.
Sidenius
Ulrik
U
Department of Analytical Chemistry, The Danish University of Pharmaceutical Sciences, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
Skonberg
Christian
C
Olsen
Jørgen
J
Hansen
Steen Honoré
SH
D000214:Acyl Coenzyme A / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid; D005978:Glutathione / Q000737:chemistry*; D006868:Hydrolysis; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013997:Time Factors
D000214:Acyl Coenzyme A; D005978:Glutathione