One- and two-electron redox chemistry of 1-carba-1-deazariboflavin

Spencer, Rob; Fisher, Jed F.; Walsh, Christopher T.

doi:10.1021/bi00635a014

Cited by 58 publications

(58 citation statements)

References 25 publications

(35 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…When IPP was added, a slight red shift to 326 nm was observed for this peak, suggesting that the coenzyme becomes protonated in the presence of IPP (33,36). Oxidized E•1-deazaFMN (µ max = 538 nm) could not be photoreduced, but reduction with 50 mM sodium dithionite yielded the anionic 1-deazaFMN red , which has a rather featureless absorbance spectrum >400 nm (37). The addition of IPP led to the formation of a species with µ max = 436 nm, also indicative of a neutral 1-deazaFMN red (37,38).…”

Section: Resultsmentioning

confidence: 99%

Evidence for the Involvement of Acid/Base Chemistry in the Reaction Catalyzed by the Type II Isopentenyl Diphosphate/Dimethylallyl Diphosphate Isomerase from Staphylococcus aureus

et al. 2008

View full text Add to dashboard Cite

The type II isopentenyl diphosphate/dimethylallyl diphosphate isomerase (IDI-2) is a flavin mononucleotide (FMN)-dependent enzyme that catalyzes the reversible isomerization of isopentenyl pyrophosphate (IPP) to dimethylallyl pyrophosphate (DMAPP), a reaction with no net change in redox state of the coenzyme or substrate. Here, UV-vis spectral analysis of the IDI-2 reaction revealed the accumulation of a reduced neutral dihydroflavin intermediate when the reduced enzyme was incubated with IPP or DMAPP. When IDI-2 was reconstituted with 1-deazaFMN and 5-deazaFMN, similar reduced neutral forms of the deazaflavin analogues were observed in the presence of IPP. Single turnover stopped-flow absorbance experiments indicated that this flavin intermediate formed and decayed at kinetically competent rates in the pre-steadystate and, thus, most likely represents a true intermediate in the catalytic cycle. UV-vis spectra of the reaction mixtures reveal trace amounts of a neutral semiquinone, but evidence for the presence of IPP-based radicals could not be obtained by EPR spectroscopy. Rapid-mix chemical quench experiments show no burst in DMAPP formation, suggesting that the rate determining step in the forward direction (IPP to DMAPP) occurs prior to DMAPP formation. A solvent deuterium kinetic isotope effect ( D 2 O V max = 1.5) was measured on v o in steady-state kinetic experiments at saturating substrate concentrations. A substrate deuterium kinetic isotope effect was also measured on the initital velocity ( D V max = 1.8) and on the decay rate of the flavin intermediate ( D k s = 2.3) in single-turnover stopped-flow experiments using (R)-[2-2 H]-IPP. Taken together, these data suggest that the C2-H bond of IPP is cleaved in the rate determining step and that general acid/ base catalysis may be involved during turnover. Possible mechanisms for the IDI-2 catalyzed reaction are presented and discussed in terms of the available X-ray crystal structures.Isoprenoids comprise a large and ubiquitous class of metabolites that participate in numerous physiological processes (1-4). All isoprenoids are derived initially from the condensation of two isoprene units, isopentenyl pyrophosphate (IPP, 1)1 and dimethylallyl pyrophosphate (DMAPP, 2). Two biosynthetic pathways for the production of IPP and DMAPP are known, the mevalonate (MVA) pathway found in animals, fungi, and archaebacteria, and the non-mevalonate or methyl erythritol phosphate (MEP) pathway † This work was supported in part by a Welch Foundation Grant (F-1511), a National Institutes of Health Grant (GM40541), and a NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript found in most eubacteria, green algae, and the chloroplasts of higher plants (1,5,6). In the MVA pathway, DMAPP must be generated from IPP by an isopentenyl diphophate/ dimethylallyl diphosphate isomerase (IDI, Scheme 1) (1). In the MEP pathway, both IPP and DMAPP are coproduced from 4-hydroxy-3-methyl-2-butenyl diphosphate in the same enzymatic reaction (catalyzed by IspH)...

show abstract

Section: Resultsmentioning

confidence: 99%

Evidence for the Involvement of Acid/Base Chemistry in the Reaction Catalyzed by the Type II Isopentenyl Diphosphate/Dimethylallyl Diphosphate Isomerase from Staphylococcus aureus

et al. 2008

View full text Add to dashboard Cite

show abstract

“…In [60]. 1 -Deaza-FADreconstituted glucose oxidase has a catalytic activity 10% that of the native enzyme, with the lower activity presumably due to the lower redox potential (E of -280 mV compared to -210 mV for FAD).…”

Section: Mechanism Probesmentioning

confidence: 98%

New flavins for old: artificial flavins as active site probes of flavoproteins

Ghisla¹,

Massey²

1986

Biochemical Journal

195

143

View full text Add to dashboard Cite

“…A solution in 0.1 M KP i (pH 7.0) was titrated with NaBH 4 until the deazaflavin was 90% reduced. Then aliquots were mixed aerobically with the same buffer, or with 2.5 mM GTN in buffer, and the course of reoxidation at 25 o C followed over a period of 3 days, care being taken to exclude light, which is known to accelerate the very slow reaction with oxygen (27). The control reaction without GTN had a t 1/2 of reoxidation of 4,600 min, and two reactions with GTN had t 1/2 values of 3,200 and 5,200 min.…”

Section: Lack Of Reactivity Of Reduced 5-deazaflavin With Gtnmentioning

confidence: 99%

Old yellow enzyme: Reduction of nitrate esters, glycerin trinitrate, and propylene 1,2-dinitrate

Meah

Brown

Chakraborty

et al. 2001

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The reaction of the old yellow enzyme and reduced flavins with organic nitrate esters has been studied. Reduced flavins have been found to react readily with glycerin trinitrate (GTN ) (nitroglycerin) and propylene dinitrate, with rate constants at pH 7.0, 25°C of 145 M ؊1 s ؊1 and 5.8 M ؊1 s ؊1 , respectively. With GTN, the secondary nitrate was removed reductively 6 times faster than the primary nitrate, with liberation of nitrite. With propylene dinitrate, on the other hand, the primary nitrate residue was 3 times more reactive than the secondary residue. In the old yellow enzyme-catalyzed NADPH-dependent reduction of GTN and propylene dinitrate, ping-pong kinetics are displayed, as found for all other substrates of the enzyme. Rapid-reaction studies of mixing reduced enzyme with the nitrate esters show that a reduced enzyme-substrate complex is formed before oxidation of the reduced flavin. The rate constants for these reactions and the apparent Kd values of the enzyme-substrate complexes have been determined and reveal that the rate-limiting step in catalysis is reduction of the enzyme by NADPH. Analysis of the products reveal that with the enzymecatalyzed reactions, reduction of the primary nitrate in both GTN and propylene dinitrate is favored by comparison with the freeflavin reactions. This preferential positional reactivity can be rationalized by modeling of the substrates into the known crystal structure of the enzyme. In contrast to the facile reaction of free reduced flavins with GTN, reduced 5-deazaflavins have been found to react some 4 -5 orders of magnitude slower. This finding implies that the chemical mechanism of the reaction is one involving radical transfers.

show abstract

One- and two-electron redox chemistry of 1-carba-1-deazariboflavin

Cited by 58 publications

References 25 publications

Evidence for the Involvement of Acid/Base Chemistry in the Reaction Catalyzed by the Type II Isopentenyl Diphosphate/Dimethylallyl Diphosphate Isomerase from Staphylococcus aureus

Evidence for the Involvement of Acid/Base Chemistry in the Reaction Catalyzed by the Type II Isopentenyl Diphosphate/Dimethylallyl Diphosphate Isomerase from Staphylococcus aureus

New flavins for old: artificial flavins as active site probes of flavoproteins

Old yellow enzyme: Reduction of nitrate esters, glycerin trinitrate, and propylene 1,2-dinitrate

Contact Info

Product

Resources

About