THE USE OF DEUTERIUM ISOTOPE EFFECTS TO PROBE THE ACTIVE SITE PROPERTIES, MECHANISM OF CYTOCHROME P450-CATALYZED REACTIONS, AND MECHANISMS OF METABOLICALLY DEPENDENT TOXICITY

• Published in: Drug metabolism and disposition Vol. 31; no. 12; pp. 1481 - 1498
• Main Authors: NELSON, Sidney D, TRAGER, William F
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Pharmacology and Experimental Therapeutics 01.12.2003
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Binding Sites; Biological and medical sciences; Catalysis; Cytochrome P-450 Enzyme System - metabolism; Deuterium - chemistry; Drug-Related Side Effects and Adverse Reactions; Enzymes and enzyme inhibitors; Fundamental and applied biological sciences. Psychology; Humans; Isotope Labeling - methods; Kinetics; Lyases; Pharmaceutical Preparations - chemistry; Pharmaceutical Preparations - metabolism; Structure-Activity Relationship; Deuterium; Isotope effect; Investigation method; Isozyme; Metabolite; Toxicity; Cytochrome P450; Active site; Reagents; Reaction mechanism; Review; Mechanism of action
• ISSN: 0090-9556; 1521-009X
• DOI: 10.1124/dmd.31.12.1481

Critical elements from studies that have led to our current understanding of the factors that cause the observed primary deuterium isotope effect, (k H /k D )obs, of most enzymatically mediated reactions to be much smaller than the “true” or intrinsic primary deuterium isotope effect, k H /k D , for the reaction are presented. This new understanding has provided a unique and powerful tool for probing the catalytic and active site properties of enzymes, particularly the cytochromes P450 (P450). Examples are presented that illustrate how the technique has been used to determine k H /k D , and properties such as the catalytic nature of the reactive oxenoid intermediate, prochiral selectivity, the chemical and enzymatic mechanisms of cytochrome P450-catalyzed reactions, and the relative active site size of different P450 isoforms. Examples are also presented of how deuterium isotope effects have been used to probe mechanisms of the formation of reactive metabolites that can cause toxic effects.