Spontaneous and reversible interaction of vanadium(V) oxyanions with amine derivatives

Crans, Debbie C.; Shin, Paul K.S.

doi:10.1021/ic00283a025

Cited by 73 publications

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“…40 Despite the 7/2 spin, line widths for 51 V are relatively narrow and are easily resolved. 41 The 51 V NMR (Figure 2), indicated that under the conditions applied in the kinetic assays the monomer concentration maximised at ~0.6 mmol L -1 . Total vanadate concentrations in the kinetic assays were chosen to yield monomer concentrations ranging from 10 µmol L -1 to 500 μmol L -1 .…”

Section: Resultsmentioning

confidence: 97%

Inhibition studies of purple acid phosphatases: implications for the catalytic mechanism

Elliott¹,

Mitić²,

Gahan³

et al. 2006

J. Braz. Chem. Soc.

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Fosfatases ácidas púrpuras (PAP) pertencem à família das metalo-hidrolases binucleares que catalisam a hidrólise de um grande grupo de substratos fosfoésteres em pH ácido. Apesar dos seus sítios ativos serem estruturamente conservados as PAP apresentam versatilidade mecanística. Neste trabalho são investigados alguns aspectos do mecanismo catalítico de duas PAP, usando os inibidores vanadato e fluoreto como sondas. Enquanto as magnitudes das constantes de inibição das duas enzimas pelo vanadato são semelhantes, as enzimas diferem com relação ao modo de inibição; vanadato interage de forma não-competitiva com a PAP de porco (K i = 40 µmol L -1 ), porém inibe a PAP de feijão competitivamente (K i = 30 µmol L -1 ). De modo semelhante, o fluoreto também age como inibidor competitivo da PAP de feijão, independentemente do pH, enquanto que o fluoreto simplesmente interage com o complexo formado pela enzima de porco e seu substrato(PAPsubstrato) em pH baixo e inibe de forma não competitiva esta enzima em pH mais alto, independentemente da composição do íon metálico. Além disso, enquanto a inibição pelo fluoreto se dá através da interação lenta com a PAP de porco, ele se liga rapidamente ao sítio catalítico da enzima do feijão. Visto que se propõe que o vanadato e o fluoreto mimetizem o estado de transição e o nucleófilo, respectivamente, as diferenças observadas na cinética de inibição indicam sutis, porém distintas diferenças no mecanismo de reação destas enzimas.Purple acid phosphatases (PAPs) belong to the family of binuclear metallohydrolases and catalyse the hydrolysis of a large group of phosphoester substrates at acidic pH. Despite structural conservation in their active sites PAPs appear to display mechanistic versatility. Here, aspects of the catalytic mechanism of two PAPs are investigated using the inhibitors vanadate and fluoride as probes. While the magnitude of their vanadate inhibition constants are similar the two enzymes differ with respect to the mode of inhibition; vanadate interacts in a non-competitive fashion with pig PAP (K i = 40 μmol L -1 ) while it inhibits red kidney bean PAP competitively (K i = 30 μmol L -1 ). Similarly, fluoride also acts as a competitive inhibitor for red kidney bean PAP, independent of pH, while the inhibition of pig PAP by fluoride is uncompetitive at low pH and non-competitive at higher pH, independent of metal ion composition. Furthermore, while fluoride acts as a slow-binding inhibitor in pig PAP it binds rapidly to the catalytic site of the red kidney bean enzyme. Since vanadate and fluoride are proposed to act as transition state and nucleophile mimics, respectively, the observed differences in inhibition kinetics indicate subtle but distinct variations in the reaction mechanism of these enzymes.Keywords: purple acid phosphatase, catalytic mechanism, kinetics, enzyme inhibition IntroductionPurple acid phosphatases (PAPs) belong to the family of binuclear metallohydrolases, with members differing widely with respect to physicochemical properties, tissue localisation...

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Section: Resultsmentioning

confidence: 97%

Inhibition studies of purple acid phosphatases: implications for the catalytic mechanism

Elliott¹,

Mitić²,

Gahan³

et al. 2006

J. Braz. Chem. Soc.

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show abstract

“…Combined potentiometric and NMR studies were particularly powerful in detailing the properties of oxovanadates [29,30], which were critical for the studies that explored the reactions of vanadium(V) in the physiological relevant pH range. Such studies were carried out by the Tracey/Gresser group [20][21][22], the Crans group [34][35][36], the Rehder group [23,37,38], and others [39][40][41].…”

Section: Studies Paving the Way For Exploration Of Aqueous Vanadium(vmentioning

confidence: 99%

“…The reaction of vanadate with ethanol [20] was the first of a series of organic systems that included numerous coordinating functionalities such as hydroxyl [20,21], carboxyl [35,48,49], amino [35,38,50,51], amido [52][53][54], phospho [22,55], and bi- [21,35,38,49,56] and multidentate [34,37,39,51,[53][54][55][57][58][59][60][61][62] ies mapped out what types of complexes formed, the pH dependence of complex formation, and the stoichiometry of the systems. This approach was followed in most subsequent studies.…”

Section: Reaction Of Vanadate With Organic Ligands In Aqueous Solutionmentioning

confidence: 99%

“…3. Thus, both the pK a of the ligand and the pK a of V 1 (H 2 VO 4 -/HVO 4 2-) contribute to give the optimal pH for complex stability [34].…”

Section: Reaction Of Vanadate With Organic Ligands In Aqueous Solutionmentioning

confidence: 99%

“…and "What is its structure?". In our first study, in which mainly 51 V NMR spectroscopy was used, we described the complexes that form between vanadate and the commonly used "good buffers" as well as a wide range of structurally related ligands [34]. This study alerted others to the problems associated with studies involving buffered vanadate solutions.…”

Section: Reaction Of Vanadate With Organic Ligands In Aqueous Solutionmentioning

confidence: 99%

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Fifteen Years of Dancing with Vanadium

Crans

2006

ChemInform

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Structures and vibrational frequencies of vanadium (V) oligomers: Anab initiostudy using effective core potentials

1996

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Spontaneous and reversible interaction of vanadium(V) oxyanions with amine derivatives

Cited by 73 publications

References 0 publications

Inhibition studies of purple acid phosphatases: implications for the catalytic mechanism

Inhibition studies of purple acid phosphatases: implications for the catalytic mechanism

Fifteen Years of Dancing with Vanadium

Structures and vibrational frequencies of vanadium (V) oligomers: Anab initiostudy using effective core potentials

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