Inhibition of type 2 isopentenyl diphosphate isomerase from Methanocaldococcus jannaschii by a mechanism-based inhibitor of type 1 isopentenyl diphosphate isomerase.
Type 2 isopentenyl diphosphate:dimethylallyl diphosphate isomerase (IDI-2, EC 5.3.3.2) is a flavoprotein, which requires FMN, NADPH, and Mg2+ for the activity to convert isopentenyl diphosphate to dimethylallyl diphosphate. For investigation of the reaction mechanism of IDI-2, 3,4-epoxy-3-methylbutyl diphosphate (EIPP), a mechanism-based inhibitor of type 1 IDI (IDI-1), was treated with the overexpressed IDI-2 (MjIDI) from methanogenic archaeon Methanocaldococcus jannaschii. EIPP showed the time- and concentration-dependent inhibition (KI; 56.5 mM, k(inact); 0.10 s(-1), k(inact)/KI; 1.76 s(-1)M(-1)) and the UV-vis spectrum of MjIDI after treatment with EIPP was apparently different from that of the untreated MjIDI. These results indicated that EIPP modified FMN through a covalent bond in the active site of MjIDI. The formed EIPP-FMN complex was separated from the reaction mixture and the spectrometric analysis of the complex suggested that the reduced form of FMN bound to EIPP at the N5 position. These results may suggest that the IDI-2 reaction is similar to IDI-1, which proceeds via carbocation-type intermediate.
Hoshino
Takeshi
T
Department of Chemistry, Tokyo Institute of Technology, O-okayama, Tokyo 152-8551, Japan.
Tamegai
Hideyuki
H
Kakinuma
Katsumi
K
Eguchi
Tadashi
T
D019748:Carbon-Carbon Double Bond Isomerases / Q000037:antagonists & inhibitors* / Q000235:genetics; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D019605:Euryarchaeota / Q000201:enzymology* / Q000235:genetics; D045782:Hemiterpenes; D007202:Indicators and Reagents; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics; D007700:Kinetics; D013058:Mass Spectrometry; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship
D004791:Enzyme Inhibitors; D045782:Hemiterpenes; D007202:Indicators and Reagents; D007527:Isoenzymes; D019748:Carbon-Carbon Double Bond Isomerases; C021453:isopentenyldiphosphate delta-isomerase