Universität zu Köln

Rokitta, Dennis, Pfeiffer, Kay, Streich, Christina, Gerwin, Henrik and Fuhr, Uwe (2013). The effect of organic solvents on enzyme kinetic parameters of human CYP3A4 and CYP1A2 in vitro. Toxicol. Mech. Methods, 23 (8). S. 576 - 584. ABINGDON: TAYLOR & FRANCIS LTD. ISSN 1537-6524

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Abstract

Enzyme kinetic parameters provide essential quantitative information about characterization of individual steps in drug metabolism. Such enzymes are located in a (partially) aqueous environment. For in vitro measurements potential lipophilic substrates regularly require organic solvents to achieve concentrations sufficient for access of the drug to the binding site of the enzyme. However, solvents may interact with the enzymes. In this study, we investigated the effects of methanol, ethanol, acetonitrile and dimethyl sulfoxide (1% to 4%) on the assessment of k(m), V-max and Cl-int for the metabolism of midazolam via CYP3A4 to 1-hydroxymidazolam and the metabolism of caffeine to paraxanthine via CYP1A2 using expressed enzymes in vitro. The presence of acetonitrile proved the highest apparent V-max value for paraxanthine formation but the lowest values for 1-hydroxymidazolam formation. The k(m) value for midazolam showed no systematic effects of organic solvents, while for caffeine k(m) was up to 8-fold lower for solvent free samples compared to solvent containing samples. The present example suggests that effects of solvents may considerably influence enzyme kinetic parameters beyond a mere change in apparent activity. These effects illustrate a difference for individual enzyme-substrate pairs, solvents, and solvent concentrations. What remains is the determination to which extent these effects compromise in vitro-in vivo extrapolations, and which solvents are most appropriate.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Rokitta, Dennis UNSPECIFIED UNSPECIFIED UNSPECIFIED Pfeiffer, Kay UNSPECIFIED UNSPECIFIED UNSPECIFIED Streich, Christina UNSPECIFIED UNSPECIFIED UNSPECIFIED Gerwin, Henrik UNSPECIFIED UNSPECIFIED UNSPECIFIED Fuhr, Uwe UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-475543
DOI:	10.3109/15376516.2013.806622
Journal or Publication Title:	Toxicol. Mech. Methods
Volume:	23
Number:	8
Page Range:	S. 576 - 584
Date:	2013
Publisher:	TAYLOR & FRANCIS LTD
Place of Publication:	ABINGDON
ISSN:	1537-6524
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language HUMAN LIVER-MICROSOMES; CYTOCHROME-P450 ISOFORMS; COCKTAIL INTERACTION; NONSPECIFIC-BINDING; DIMETHYL-SULFOXIDE; METABOLISM; INHIBITION; MECHANISM; SUBSTRATE; MIDAZOLAM Multiple languages Toxicology Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/47554