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Statements

Subject Item
n2:RIV%2F00209805%3A_____%2F13%3A%230000425%21RIV14-GA0-00209805
rdf:type
skos:Concept n9:Vysledek
rdfs:seeAlso
http://dx.doi.org/10.1016/j.aca.2013.06.014
dcterms:description
It was originally shown that urease retains its enzymatic activity when adsorbed at bare mercury and solid amalgam surfaces. However the opinion later prevailed that, when adsorbed at bare metal electrodes, proteins are irreversibly denatured. Here we confirm that urease is enzymatically active at a bare solid amalgam surface as found by Santhanam et al., and we show that this enzyme is equally active at a thiol-modified amalgam surface. We also show that it is the reduced form of urease, which is enzymatically active at Hg surfaces. Oxidation of the protein, resulting in formation of disulfide bonds, strongly decreases the enzyme activity. Using constant current chronopotentiometric stripping (CPS) we show that the exposure of surface-attached urease to negative potentials results in the protein unfolding. The extent of the unfolding depends upon the amount of time for which the protein is exposed to negative potentials, and at very short times this unfolding can be avoided. At thiol-modified Hg surfaces the protein is less vulnerable to the effects of the electric field. We conclude that the loss of enzymatic activity, resulting from a 10 min exposure of the protein to -0.58 V, is not due to reduction of the disulfide bonds as suggested by Santhanam et al. This loss is probably a result of protein reorientation, due to reduction of the Hg-S bonds (formed by accessible cysteines), followed by prolonged electric field effect on the surface-attached protein. It was originally shown that urease retains its enzymatic activity when adsorbed at bare mercury and solid amalgam surfaces. However the opinion later prevailed that, when adsorbed at bare metal electrodes, proteins are irreversibly denatured. Here we confirm that urease is enzymatically active at a bare solid amalgam surface as found by Santhanam et al., and we show that this enzyme is equally active at a thiol-modified amalgam surface. We also show that it is the reduced form of urease, which is enzymatically active at Hg surfaces. Oxidation of the protein, resulting in formation of disulfide bonds, strongly decreases the enzyme activity. Using constant current chronopotentiometric stripping (CPS) we show that the exposure of surface-attached urease to negative potentials results in the protein unfolding. The extent of the unfolding depends upon the amount of time for which the protein is exposed to negative potentials, and at very short times this unfolding can be avoided. At thiol-modified Hg surfaces the protein is less vulnerable to the effects of the electric field. We conclude that the loss of enzymatic activity, resulting from a 10 min exposure of the protein to -0.58 V, is not due to reduction of the disulfide bonds as suggested by Santhanam et al. This loss is probably a result of protein reorientation, due to reduction of the Hg-S bonds (formed by accessible cysteines), followed by prolonged electric field effect on the surface-attached protein.
dcterms:title
Enzymatic activity and catalytic hydrogen evolution in reduced and oxidized urease at mercury surfaces Enzymatic activity and catalytic hydrogen evolution in reduced and oxidized urease at mercury surfaces
skos:prefLabel
Enzymatic activity and catalytic hydrogen evolution in reduced and oxidized urease at mercury surfaces Enzymatic activity and catalytic hydrogen evolution in reduced and oxidized urease at mercury surfaces
skos:notation
RIV/00209805:_____/13:#0000425!RIV14-GA0-00209805
n9:predkladatel
n10:ico%3A00209805
n3:aktivita
n4:P n4:I n4:Z
n3:aktivity
I, P(ED2.1.00/03.0101), P(GA13-00956S), P(GAP301/11/2055), Z(AV0Z50040702)
n3:cisloPeriodika
July
n3:dodaniDat
n16:2014
n3:domaciTvurceVysledku
n21:9991646
n3:druhVysledku
n11:J
n3:duvernostUdaju
n14:S
n3:entitaPredkladatele
n17:predkladatel
n3:idSjednocenehoVysledku
73074
n3:idVysledku
RIV/00209805:_____/13:#0000425
n3:jazykVysledku
n18:eng
n3:klicovaSlova
urease enzymatic activity; constant-current chronopotentiometric stripping; mercury containing electrodes; thiol-modified electrodes; protein structure at surfaces; protein denaturation at negatively charged surface
n3:klicoveSlovo
n7:constant-current%20chronopotentiometric%20stripping n7:thiol-modified%20electrodes n7:urease%20enzymatic%20activity n7:protein%20denaturation%20at%20negatively%20charged%20surface n7:protein%20structure%20at%20surfaces n7:mercury%20containing%20electrodes
n3:kodStatuVydavatele
NL - Nizozemsko
n3:kontrolniKodProRIV
[B16F76A2C033]
n3:nazevZdroje
Analytica Chimica Acta
n3:obor
n13:CG
n3:pocetDomacichTvurcuVysledku
1
n3:pocetTvurcuVysledku
3
n3:projekt
n6:GA13-00956S n6:GAP301%2F11%2F2055 n6:ED2.1.00%2F03.0101
n3:rokUplatneniVysledku
n16:2013
n3:svazekPeriodika
789
n3:tvurceVysledku
Paleček, Emil
n3:wos
000322610600004
n3:zamer
n15:AV0Z50040702
s:issn
0003-2670
s:numberOfPages
5
n5:doi
10.1016/j.aca.2013.06.014