Fluorine nuclear magnetic resonance studies of biological systems: Part~1. Investigation of the binding of a fluorinated boronic acid transition state analog to alpha-chymotrypsin. Part~2. Fluorine NMR study of the metabolism of m-trifluoromethyl-alpha-ethyl benzhydrol (flumecinol).

摘要

Part 1. Serine proteases share a number of common structural features including the presence of an essential serine residue at the catalytic site. Boronic acids interact strongly with these enzymes to inactivate them, presumably by a process that involves formation of a species that resembles the critical transition state produced during the hydrolysis of substrates by the enzyme. {dollar}sp{lcub}19{rcub}{dollar}F NMR relaxation and Overhauser effect data obtained at 282 and 470 MHz have been used to obtain information about the nature of the complex formed between (R)-1-acetamido-2(p-F-phenyl)ethane boronic acid and the serine protease {dollar}alpha{dollar}-chymotrypsin at pH 4 and 7. A theoretical model based on these NMR parameters has been constructed and used to define the correlation time characteristic of the motion of the fluoroaromatic ring in the complex.; Part 2. Metabolism of the drug Flumecinol, a compound in clinical trial for use in humans as an inducer of liver function, has been examined in young rats using a variety of experimental techniques, including fluorine NMR analysis of urinary metabolites and observations of the metabolic process in vivo by means of localized fluorine NMR spectroscopy. Using these techniques the time course of the formation of the metabolites in urine has been monitored revealing a dose dependency in the metabolites produced. The in vivo studies have provided an indication of the time scale for processing the drug by the liver. It appears that Flumecinol is accumulated by the liver almost immediately after ingestion while the compound and its metabolites are still present after up to 20 hours, even in the livers of animals that have been previously induced with Flumecinol or Phenobarbital. The resolution of the fluorine spectra obtained from the living animals was not sufficient to quantitate individual metabolites. There was no evidence from nuclear Overhauser effect studies for binding of drug or metabolites to cellular proteins, and these materials appear to remain entirely in the cytoplasm.