scholarly journals Role of hydrogen in the activation and regulation of hydrogen oxidation by the soluble hydrogenase from Alcaligenes eutrophus H16

1988 ◽  
Vol 254 (2) ◽  
pp. 463-468 ◽  
Author(s):  
M R Hyman ◽  
C A Fox ◽  
D J Arp
Keyword(s):  
Hydrogen Oxidation ◽  
Alcaligenes Eutrophus ◽  
Constant Concentration ◽  
Activation Kinetics ◽  
Diaphorase Activity ◽  
Alcaligenes Eutrophus H16 ◽  
Level Of Activity ◽  
H2 Oxidation ◽  
Kinetics Of

The activation kinetics of the H2-oxidizing activity of the soluble hydrogenase from Alcaligenes eutrophus H16 were investigated. Activation with Na2S2O4 plus 101 kPa H2 resulted in a rapid increase in activity over 1 h and constant activity after 3 h incubation. Less-stable activations were achieved if enzyme was incubated with Na2S2O4 under 1 kPa H2 or 101 kPa N2. The enzyme could also be partly activated either with NADH alone or with H2 alone. The level of activity obtained with both 101 kPa H2 and NADH present was greater than that obtained with either 101 kPa H2 or NADH alone. Activation with H2 plus NADH was virtually independent of NADH concentration but highly dependent on H2 concentration. The effects of various concentrations of H2 and constant concentration of NADH on the level of activation were the same whether H2 oxidation was assayed by H2-dependent Methylene Blue or NAD+ reduction. Diaphorase activity did not require activation and was little affected by the treatments that activated H2-oxidizing activity. The results suggest that H2 plays an important role in regulating the level of H2-oxidizing activity in this soluble hydrogenase.

scholarly journals Reversible and irreversible effects of nitric oxide on the soluble hydrogenase from Alcaligenes eutrophus H16

1988 ◽  
Vol 254 (2) ◽  
pp. 469-475 ◽  
Author(s):  
M R Hyman ◽  
D J Arp
Keyword(s):  
Electron Acceptor ◽  
Alcaligenes Eutrophus ◽  
Irreversible Inhibition ◽  
Diaphorase Activity ◽  
Alcaligenes Eutrophus H16 ◽  
Binding Inhibition ◽  
Irreversible Effects ◽  
Irreversible Effect ◽  
Sites Of Action ◽  
H2 Oxidation

The effects of NO on the H2-oxidizing and diaphorase activities of the soluble hydrogenase from Alcaligenes eutrophus H16 were investigated. With fully activated enzyme, NO (8-150 nM in solution) inhibited H2 oxidation in a time- and NO-concentration-dependent process. Neither H2 nor NAD+ appeared to protect the enzyme against the inhibition. Loss of activity in the absence of an electron acceptor was about 10 times slower than under turnover conditions. The inhibition was partially reversible; approx. 50% of full activity was recoverable after removal of the NO. Recovery was slower in the absence of an electron acceptor than in the presence of H2 plus an electron acceptor. The diaphorase activity of the unactivated hydrogenase was not affected by NO concentrations of up to 200 microM in solution. Exposure of the unactivated hydrogenase to NO irreversibly inhibited the ability of the enzyme to be fully activated for H2-oxidizing activity. The enzyme also lost its ability to respond to H2 during activation in the presence of NADH. The results are interpreted in terms of a complex inhibition that displays elements of (1) a reversible slow-binding inhibition of H2-oxidizing activity, (2) an irreversible effect on H2-oxidizing activity and (30 an irreversible inhibition of a regulatory component of the enzyme. Possible sites of action for NO are discussed.

scholarly journals Functional and Structural Role of the Cytochrome b Subunit of the Membrane-Bound Hydrogenase Complex of Alcaligenes Eutrophus H16

1997 ◽  
Vol 248 (1) ◽  
pp. 179-186 ◽  
Author(s):  
Michael Bernhard ◽  
Bruna Benelli ◽  
Alejandro Hochkoeppler ◽  
Davide Zannoni ◽  
Barbel Friedrich
Keyword(s):  
Cytochrome B ◽  
Alcaligenes Eutrophus ◽  
Structural Role ◽  
B Subunit ◽  
Alcaligenes Eutrophus H16 ◽  
Membrane Bound

The role of ruthenium in improving the kinetics of hydrogen oxidation and evolution reactions of platinum

2021 ◽  
Author(s):  
Shangqian Zhu ◽  
Xueping Qin ◽  
Fei Xiao ◽  
Shuangli Yang ◽  
Yuan Xu ◽  
...  
Keyword(s):  
Hydrogen Oxidation ◽  
Kinetics Of

scholarly journals Functional role of the polysaccharide component of rabbit thrombomodulin proteoglycan. Effects on inactivation of thrombin by antithrombin, cleavage of fibrinogen by thrombin and thrombin-catalysed activation of factor V

1990 ◽  
Vol 270 (2) ◽  
pp. 419-425 ◽  
Author(s):  
M C Bourin ◽  
U Lindahl
Keyword(s):  
Protein C ◽  
Inhibitory Effect ◽  
Factor V ◽  
Promoting Effect ◽  
Activation Kinetics ◽  
Polysaccharide Chain ◽  
Factor Va ◽  
Kinetics Of ◽  
Similar Sample

Thrombomodulin (TM), a major anticoagulant protein at the vessel wall, serves as a potent cofactor for the activation of Protein C by thrombin. Previous work has indicated that (rabbit) TM is a proteoglycan that contains a single polysaccharide chain, tentatively identified as a sulphated galactosaminoglycan, and furthermore suggested that this component may be functionally related to additional anticoagulant activities expressed by the TM molecule [Bourin, Ohlin, Lane, Stenflo & Lindahl (1988) J. Biol. Chem. 263, 8044-8052]. Results of the present study establish that (enzymic) removal of the polysaccharide chain abolishes the inhibitory effect of TM on thrombin-induced fibrinogen clotting as well as the promoting effect of TM on the inactivation of thrombin by antithrombin, but does not affect the ability of TM to serve as a cofactor in the activation of Protein C. Studies of yet another biological activity of rabbit TM, namely the ability to prevent the activation of Factor V by thrombin [Esmon, Esmon & Harris (1982) J. Biol. Chem. 257, 7944-7947], confirmed that TM markedly delays the conversion of the native 330 kDa Factor V precursor into polypeptide intermediates, and further into the 96 kDa heavy chain and 71-74 kDa light-chain components of activated Factor Va. In contrast, the activation kinetics of a similar sample of Factor V incubated with thrombin in the presence of chondroitinase ABC-digested TM did not differ from that observed in the absence of TM. It is concluded that the inhibitory effect of TM on Factor V activation also depends on the presence of the polysaccharide component on the TM molecule.

On the relationship between affinity for molecular hydrogen and the physiological directionality of hydrogenases

2005 ◽  
Vol 33 (1) ◽  
pp. 12-14 ◽  
Author(s):  
D.J. van Haaster ◽  
P.-L. Hagedoorn ◽  
J.A. Jongejan ◽  
W.R. Hagen
Keyword(s):  
Molecular Hydrogen ◽  
Pyrococcus Furiosus ◽  
Hydrogen Oxidation ◽  
Desulfovibrio Vulgaris ◽  
Proton Reduction ◽  
Hydrogen Activation ◽  
The Relationship ◽  
H2 Oxidation ◽  
Kinetics Of

The physiological significance of the generic reaction H2↔2[H] is not always clear because hydrogenases may function in the breakdown of molecular hydrogen or in its synthesis or in both directions. Fe-hydrogenases have nevertheless been most often associated with proton reduction and NiFe-hydrogenases with hydrogen oxidation. A re-determination of the KM of H2 oxidation by Pyrococcus furiosus NiFe-hydrogenase-I and by Desulfovibrio vulgaris Fe-hydrogenase suggests that affinity for hydrogen has been seriously underestimated and that the kinetics of hydrogen activation in relation to the directionality of hydrogenases should be re-evaluated.

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