Application of the critical precipitation assay to complex samples: aluminium binding capacity of human gastrointestinal fluids

Powell, Jonathan J.; Jugdaohsingh, Ravin; Piotrowicz, Andrew; White, Kenneth; McCrohan, Catherine R.; Thompson, R. P. H.

doi:10.3184/095422904782775045

Cited by 2 publications

(2 citation statements)

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“…Binding of Al 3þ ion with ATP is stronger than with Mg 2 þ , which is a natural activator of ATP-ase; therefore the Al 3þ ion is a strong inhibitor of all ATP-ases. It has been documented that Al 3þ inhibits activity of hexokinase, adenylat-cyclase, calmodulin, NAD-kinase and other Mg-dependent enzymes [33]. In addition, there is lack of data referring about mechanism and kinetics of aluminium binding to gastrointestinal fluids, especially to main enzyme of gastric juice -pepsin.…”

Section: Discussionmentioning

confidence: 99%

The influence of Al³⁺ion on porcine pepsin activityin vitro

Pavelkić¹,

Gopčević

Krstić

et al. 2008

Journal of Enzyme Inhibition and Medicinal Chemistry

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The in vitro effect of Al 3þ ions in the concentration range 1.7·10 26 M -8.7·10 23 M on pepsin activity at pH 2, via kinetic parameters and its electrophoretic mobility was evaluated. Kinetic study demonstrated the existence of an activation effect of Al 3þ at pH 2 on pepsin molecule. Kinetic analysis with respect to concentrations of haemoglobin showed that Al 3þ ions increase the maximal velocity (V max ) and k cat values rather than apparent affinity for substrate (K S ) implying the non-competitive nature of activation which indicated that aluminium was a non-essential activator of partial non-competitive type. The values of the equilibrium constants K S and K mA for dissociation of corresponding complexes were evaluated as 0.904^0.083 mM and 8.56^0.51 mM, respectively. Dissociation constant K A , of activator from enzyme-activator complex calculated via kinetic and direct measurement of Al 3þ binding data, as well as activation constant A 50 , the activator concentration that gives a rate equal to half at a saturating concentration of activator, were found to be 8.82^0.90 mM, 8.39^0.76 mM, and 8.05^0.48 mM respectively. Native PAGE electrophoresis shows the decrease in electrophoretic mobility of pepsin and confirms modification of the electric charge and conformational changes of pepsin caused by bound Al 3þ on the pepsin molecule. Al 3þ induced conformational changes of pepsin were verified by UV-VIS and IR spectra. Moreover, the absence of conformational changes in the haemoglobin molecule in the presence of Al 3þ ions confirms that the obtained activation is a consequence of conformational changes caused only in the pepsin molecule.

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Section: Discussionmentioning

confidence: 99%

The influence of Al³⁺ion on porcine pepsin activityin vitro

Pavelkić¹,

Gopčević

Krstić

et al. 2008

Journal of Enzyme Inhibition and Medicinal Chemistry

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show abstract

“…Thus, in spite of such differences, rapid non-equilibrium conditions do approximate to equilibrium but, moreover, there is an empirical value of this assay to investigate Al-ligand interactions that must better represent most "real" conditions. We, for example, have applied this assay to determine the Al binding capacity of gastrointestinal fluids in some following work (Powell et al, 2004).…”

Section: Discussionmentioning

confidence: 99%