L. Korsgaard Christensen

INHIBITION OF DRUG METABOLISM BY CHLORAMPHENICOL

Abstract Chloramphenicol has been shown to retard the biotransformation of tolbutamide, diphenylhydantoin, and dicoumarol in man. Treatment with 2 g. of chloramphenicol for some days resulted in a rise in the concentration of tolbutamide and diphenylhydantoin in blood. The half-life values of tolbutamide, diphenylhydantoin, and dicoumarol in blood increased very considerably after chloramphenicol. A case of chloramphenicol-induced hypoglycaemic collapse in a tolbutamide-treated patient is reported.

Concerning the pH optimum of peptic hydrolysis

Abstract The significance of hydrogen-ion concentration to peptic hydrolysis of a number of proteins has been studied in order to throw light upon certain aspects of the activity vs. pH curves. Various denatured substrates are readily hydrolyzed within a wide pH interval. The more “unfolded” the substrate molecule is, the less does the rate of peptic hydrolysis depend on the hydrogenion concentration. In the case of a native substrate (egg albumin), the pH optimum is in the strongly acid range, around pH 0.8–1. At pH values exceeding 1.5–2, the rate of hydrolysis is rather slow. Thus there is a considerable difference between the pH curves for hydrolysis of a native substrate and the corresponding denatured one. This supports the view that the first step in hydrolysis of a native protein consists in an “unfolding” of the peptide chains of the molecule.

Analytical use of the protein-dissolving effect of urea.

Abstract The capacity of strong urea solutions to dissolve protein precipitates may be utilized for determination of protein concentrations by ultraviolet absorbancy measurement since urea itself has a very low absorption at the wavelength employed. This can serve as a basis for methods of determining peptic or tryptic hydrolysis. These procedures are useful for determination of proteolytic activity of media with high contents of extraneous protein or of nonprotein substances having a high ultraviolet absorbancy.