Electrospray Ionization Mass Spectrometric Analysis of Intact Cytochrome P450: Identification of Tienilic Acid Adducts to P450 2C9

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• 作者：Luke L. Koenigs ; Raimund M. Peter ; Ann P. Hunter ; Robert L. Haining ; Allan E. Rettie ; Thomas Friedberg ; Michael P. Pritchard ; Magang Shou ; Thomas H. Rushmore ; and William F. Trager
• 刊名：Biochemistry
• 出版年：1999
• 出版时间：February 23, 1999
• 年：1999
• 卷：38
• 期：8
• 页码：2312 - 2319
• 全文大小：96K
• 年卷期：v.38,no.8(February 23, 1999)
• ISSN：1520-4995

文摘

A general scheme for the purification of baculovirus-expressed cytochrome P450s (P450s)from the crude insect cell pastes has been designed which renders the P450s suitable for analysis byhigh-performance liquid chromatography (HPLC) electrospray ionization mass spectrometry (ESI-MS).An HPLC/ESI-MS procedure has been developed to analyze small amounts of intact purified P450 (P450scam-HT, 1A1, 1A2, 2A6, 2B1, 2C9, 2C9 C175R, 3A4, 3A4-HT) and rat NADPH cytochrome P450reductase (P450 reductase). The experimentally determined and predicted (based on the amino acidsequences) molecular masses (MMs) of the various proteins had identical rank orders. For each individualprotein, the difference between the experimentally determined (±SD, based on experiments performedon at least 3 different days) and predicted MMs ranged from 0.002 to 0.035%. Each experimentallydetermined MM had a standard deviation of less than 0.09% (based on the charge state distribution).Application of this HPLC/ESI-MS technique made the detection of the covalent modification to P4502C9 following mechanism-based inactivation by tienilic acid possible. In the absence of glutathione, threeP450 2C9 species were detected that produced ESI mass spectra corresponding to native P450 2C9 andboth a monoadduct and a diadduct of tienilic acid to P450 2C9. In the presence of glutathione, onlynative P450 2C9 and the monoadduct were detected. Based on the observed mass shifts for the P4502C9/tienilic acid adducts, a mechanism for the inactivation of P450 2C9 by tienilic acid is proposed.