Characterization of Isoleucyl-tRNA Synthetase from Staphylococcus aureus

Pope, Andrew J.; Moore, Keith J. M.; McVey, Mary; Mensah, Lucy; Benson, Neil; Osbourne, Neal; Broom, Nigel J. P.; Brown, Murray J. B.; O’Hanlon, Peter J.

doi:10.1074/jbc.273.48.31691

Cited by 59 publications

(45 citation statements)

References 31 publications

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“…5, using Grafit (version 5) for each inactivator concentration. This regression simultaneously estimates the apparent rate constant for the formation of the final steady state equilibrium (K obs ) plus the initial and steady state velocities of product formation (V 0 and V s ) for each curve analyzed (Morrison and Walsh, 1988;Pope et al, 1998).…”

Section: Methodsmentioning

confidence: 99%

“…Progress curve analysis uses an "all-in" approach where the enzyme is exposed simultaneously to probe substrate and inactivator/inhibitor while enzyme activity is monitored throughout the inactivation. This type of analysis has long been an accepted tool for measuring presteady state kinetics for a variety of physiological enzymes (Orson and Tipton, 1979;Pope et al, 1998;Maurer et al, 2000;Dash et al, 2001). However, its use in the context of P450 inactivation is unprecedented.…”

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confidence: 99%

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Progress Curve Analysis of CYP1A2 Inhibition: A More Informative Approach to the Assessment of Mechanism-Based Inactivation?

Fairman¹,

Collins²,

Chapple³

2007

Drug Metab Dispos

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ABSTRACT:Mechanism-based cytochrome P450 inactivation is defined as a time-and NADPH-dependent inactivation that is not reversible upon extensive dialysis. Current methodologies use dilution approaches to estimate the rate of inactivation and offer limited mechanistic insight and are significantly influenced by experimental conditions. We investigated the potential of progress curve analysis because this experimental design allows investigation of both the reversible (K iapp ) and irreversible (K i , K inact ) components of the reaction mechanism. The human liver microsomal CYP1A2 inactivation kinetics of resveratrol, oltipraz, furafylline, and dihydralazine (Fig. 2) ). This range of estimates highlights the potential caveats surrounding the existing methodologies that have been previously discussed in depth. In addition to these inactivation parameters, we have been able to demonstrate a variation in balance of reversible versus irreversible inhibition within these inactivators. Oltipraz and resveratrol have K iapp values similar to their K i , indicating a significant early onset reversible inhibition, whereas furafylline and dihydralazine are dominated by irreversible inactivation. This approach allows a more mechanistic investigation of an inactivator and in the future may improve the prediction of clinical drug-drug interactions.Clinical drug-drug interactions (DDIs) can pose significant challenges to the development of novel chemical entities into marketable agents. Novel chemical entities may become victims to interactions that increase their maximal plasma concentration or plasma area under the curve and reduce their therapeutic index or alternatively cause increases in exposure and erode the therapeutic index of coadministered drugs. The most common DDIs are likely due to reversible inhibition of hepatic cytochrome P450 enzymes (P450s) (Lin and Lu, 1998). Alternatively, a more complex process can occur where drugs are metabolized into intermediates that can irreversibly inactivate P450s. This is known as mechanism-based inactivation (MBI) and results in a dose-and time-dependent loss of P450 activity (Silverman, 1995). Subsequent recovery of P450 activity is entirely due to de novo synthesis of P450 protein. This process leads to a significant delay between withdrawal of the inactivator and recovery of metabolism. An example of a mechanism-based clinical DDI involving CYP1A2 is the interaction between furafylline and caffeine, where coadministration increased the plasma area under the curve of caffeine 7-to 10-fold accompanied by significant incidence of unacceptable side effects (Tarrus et al., 1987).Significant success has been achieved in the prediction of clinical DDI from in vitro analysis of reversible P450 inhibitors (Brown et al., 2005;Ito et al., 2005;Obach et al., 2006). These methodologies allow accurate estimation of the likely magnitude of DDI using relatively simple in vitro techniques and scaling to humans using physiological parameters such as hepatic blood flow and plasma unbound fract...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Progress Curve Analysis of CYP1A2 Inhibition: A More Informative Approach to the Assessment of Mechanism-Based Inactivation?

Fairman¹,

Collins²,

Chapple³

2007

Drug Metab Dispos

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“…Pseudomonic acid has been hypothesized to be an analogue of IleRS small substrates or intermediate isoleucyl-AMP (2,4,23,25). The mode of action of pseudomonic acid has been compared in detail with those of isoleucyl-AMP analogues (49). Recent crystallographic analysis of T. thermophilus IleRS complexed with the isoleucyl-AMP analogue suggested that the antibiotic blocks the binding of active intermediate isoleucyl-AMP (24).…”

Section: Fig 6 P Fluorescensmentioning

confidence: 99%

How Does Pseudomonas fluorescens Avoid Suicide from Its Antibiotic Pseudomonic Acid?

Yanagisawa

Kawakami²

2003

Journal of Biological Chemistry

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Two isoleucyl-tRNA synthetases (IleRSs) encoded by two distinct genes (ileS1 and ileS2) were identified in pseudomonic acid (mupirocin)-producing Pseudomonas fluorescens. The most striking difference between the two IleRSs (IleRS-R1 and IleRS-R2) is the difference in their abilities to resist pseudomonic acid. Purified IleRS-R2 showed no sensitivity to pseudomonic acid even at a concentration of 5 mM, 10 5 times higher than the K i value of IleRS-R1. The amino acid sequence of IleRS-R2 exhibits eukaryotic features that are originally found in eukaryotic proteins. Escherichia coli cells transformed with the ileS2 gene exerted pseudomonic acid resistance more than did those transformed with ileS1. Cells transformed with both genes became almost as resistant as P. fluorescens. These results suggest that the presence of IleRS-R2 could be the major reason why P. fluorescens is intrinsically resistant to the antibiotic. Here we suggest that the evolutionary scenario of the eukaryotic ileS2 gene can be explained by gene acquisition and that the pseudomonic acid producer may have maintained the ileS2 gene to protect itself from pseudomonic acid.

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“…For example, the antibiotic mupirocin 3 ( Figure 6) exerts its action by selectively inhibiting prokaryotic isoleucyl-tRNA synthetases (145,146), and phosmidosine 4 ( Figure 6) (147, 148) likely inhibits prolyltRNA synthetase by effectively mimicking the acyladenylate intermediate formed by this enzyme. These findings therefore resulted in the development of efficient synthetic routes for preparing chemically stable analogs of acyladenylates (148)(149)(150) in the expectation that such compounds will exhibit antibacterial activity coupled with low mammalian toxicity (151,152). In light of these studies (145)(146)(147)(148)(149)(150), β-asparaginyladenylate 5 ( Figure 6) was synthesized (153) The relatively lengthy synthetic route to obtain this compound and the presence of a charged phosphoamidate functional group argue against its likely clinical utility.…”

Section: Sulfonamide Derivatives As Inhibitors Of Human Asparagine Symentioning

confidence: 99%

Asparagine Synthetase Chemotherapy

Richards

Kilberg

2006

Annu. Rev. Biochem.

202

221

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Modern clinical treatments of childhood acute lymphoblastic leukemia (ALL) employ enzymebased methods for depletion of blood asparagine in combination with standard chemotherapeutic agents. Significant side effects can arise in these protocols and, in many cases, patients develop drug-resistant forms of the disease that may be correlated with up-regulation of the enzyme glutamine-dependent asparagine synthetase (ASNS). Though the precise molecular mechanisms that result in the appearance of drug resistance are the subject of active study, potent ASNS inhibitors may have clinical utility in treating asparaginase-resistant forms of childhood ALL. This review provides an overview of recent developments in our understanding of (a) the structure and catalytic mechanism of ASNS, and (b) the role that ASNS may play in the onset of drug-resistant childhood ALL. In addition, the first successful, mechanism-based efforts to prepare and characterize nanomolar ASNS inhibitors are discussed, together with the implications of these studies for future efforts to develop useful drugs.

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Characterization of Isoleucyl-tRNA Synthetase from Staphylococcus aureus

Abstract: The interactions of isoleucyl-tRNA synthetase (IleRS,E

Cited by 59 publications

References 31 publications

Progress Curve Analysis of CYP1A2 Inhibition: A More Informative Approach to the Assessment of Mechanism-Based Inactivation?

Progress Curve Analysis of CYP1A2 Inhibition: A More Informative Approach to the Assessment of Mechanism-Based Inactivation?

How Does Pseudomonas fluorescens Avoid Suicide from Its Antibiotic Pseudomonic Acid?

Asparagine Synthetase Chemotherapy

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