The reaction of <i>Pseudomonas aeruginosa</i> cytochrome <i>c</i> oxidase with carbon monoxide

Parr, S R; Wilson, Michael T.; Greenwood, C. T.

doi:10.1042/bj1510051

Cited by 62 publications

(44 citation statements)

References 16 publications

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“…The present kinetic results do not allow us to say which haem, c or dl, is the binding site for oxygen, but ligand-binding evidence (Parr et al, 1975;1978 . This behaviour would therefore appear to parallel that of mammalian cytochrome c oxidase (Gibson et al, 1965;Greenwood & Gibson, 1967), in which the presence of the substrate, oxygen, greatly increased the electron-transfer rates within the protein, although it is clear that the rate of oxygen reduction by the bacterial enzyme is very much lower than that…”

Section: Discussionmentioning

confidence: 74%

“…Ligand-binding studies on the reduced enzyme have shown that both CO and cyanide bind to the haem d1 component (Parr et al, 1975;, and on this basis it has been assumed that this particular redox centre is also the site of attack by oxygen. Two previous attempts at understanding the detailed mechanism of the reaction of Pseudomonas cytochrome oxidase with oxygen have been reported. Shimada & Orii (1976) have used rapid-scanning spectrophotometry to observe the reduction of the enzyme by excess ascorbate in the presence of oxygen.…”

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confidence: 99%

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The reaction of Pseudomonas aeruginosa cytochrome c-551 oxidase with oxygen

Greenwood¹,

Barber²,

Parr³

et al. 1978

Biochemical Journal

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The reaction of ascorbate-reduced Pseudomonas cytochrome oxidase with oxygen was studied by using stopped-flow techniques at pH 7.0 and 25°C. The observed time courses were complex, the reaction consisting of three phases. Of these, only the fastest process, with a second-order rate constant of 3.3 x 104 M-1 S-s, was dependent on oxygen concentration. The two slower processes were first-order reactions with rates of 1.0 ± 0.4s-' and 0.1 ±0.03s-'. A kinetic titration experiment revealed that the enzyme had a relatively low affinity constant for oxygen, approx. 1 0 M-1. Kinetic difference spectra were determined for all three reaction phases, showing each to have different characteristics. The fast-phase difference spectrum showed that changes occurred at both the haem c and haem di components of the enzyme during this process. These changes were consistent with the haem c becoming oxidized, but with the haem d1 assuming a form that did not correspond to the normal oxidized state, a situation that was not restored even after the second kinetic phase, which reflected further changes in the haem d1 component. The results are discussed in terms of a kinetic scheme.

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Section: Discussionmentioning

confidence: 74%

mentioning

confidence: 99%

The reaction of Pseudomonas aeruginosa cytochrome c-551 oxidase with oxygen

Greenwood¹,

Barber²,

Parr³

et al. 1978

Biochemical Journal

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“…The kinetics of NO release from the fully reduced NO-bound wild type cd 1 NIR is biphasic with values of 35 and 6 s Ϫ1 at pH 7.0 (average from values listed in Table 1). Although the biphasicity is not understood at present, it might be related to the dimeric structure of the enzyme, which has been previously shown to display cooperative behavior with some ligands, such as CO (20) and cyanide (24). An intrinsic functional asymmetry of the enzyme is also evident in the reaction with macromolecular electron donors (such as azurin and cytochrome c551) (27,28) and in the intramolecular electron transfer step (29).…”

Section: Discussionmentioning

confidence: 99%

Fast Dissociation of Nitric Oxide from Ferrous Pseudomonas aeruginosa cd1 Nitrite Reductase

Rinaldo¹,

Arcovito

Brunori

et al. 2007

Journal of Biological Chemistry

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The heme-containing periplasmic nitrite reductase (cd 1 NIR) is responsible for the production of nitric oxide (NO) in denitrifying bacterial species, among which are several animal and plant pathogens. Heme NIRs are homodimers, each subunit containing one covalently bound c-heme and one d 1 -heme. The reduction of nitrite to NO involves binding of nitrite to the reduced protein at the level of d 1 -heme, followed by dehydration of nitrite to yield NO and release of the latter. The crucial ratelimiting step in the catalytic mechanism is thought to be the release of NO from the d 1 -heme, which has been proposed, but never demonstrated experimentally, to occur when the iron is in the ferric form, given that the reduced NO-bound derivative was presumed to be very stable, as in other hemeproteins. We have measured for the first time the kinetics of NO binding and release from fully reduced cd 1 NIR, using the enzyme from Pseudomonas aeruginosa and its site-directed mutant H369A. Quite unexpectedly, we found that NO dissociation from the reduced d 1 -heme is very rapid, several orders of magnitude faster than that measured for b-type heme containing reduced hemeproteins. Because the rate of NO dissociation from reduced cd 1 NIR, measured in the present report, is faster than or comparable with the turnover number, contrary to expectations this event may well be on the catalytic cycle and not necessarily rate-limiting. This finding also provides a rationale for the presence in cd 1 NIR of the peculiar d 1 -heme cofactor, which has probably evolved to ensure fast product dissociation.Pseudomonas aeruginosa, a facultative anaerobe, can use denitrification as the anaerobic energy-producing pathway (1). This microorganism is an opportunistic pathogen, and it has been shown that, in the host, the denitrification pathway not only works as a source of electrons (2) but may also be involved in nitric oxide (NO) 2 scavenging, given that the classical flavohemoglobin-mediated detoxification pathway is not active (3). More recently, low concentrations of NO have also been shown to control the lifestyle of P. aeruginosa by inducing dispersal of the multicellular assemblies (biofilms) strictly related to chronic pulmonary infections (4). Therefore, pathogenesis, NO metabolism, and denitrification are strictly related.The conversion of nitrite (NO 2 Ϫ ) to nitric oxide (NO) is catalyzed in denitrifying bacteria by the periplasmic nitrite reductases (NIR), which are either copper-or heme-containing enzymes (5). P. aeruginosa NIR belongs to the latter type, being a homodimer of two 60-kDa subunits, each containing one covalently bound c-heme and one d 1 -heme. Extensive spectroscopic and functional studies have been carried out on cd 1 NIRs (5, 6); the c-heme domain is the entry site of the electrons, whereas catalysis occurs at the level of the d 1 -heme.The established physiological role of these enzymes is to catalyze the one-electron reduction of NO 2 Ϫ to NO. The reaction cycle involves binding of nitrite to the reduced protein...

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“…[41][42][43][44][45][46][47][48][49] Many date from the days when the enzyme was referred to as "bacterial cytochrome oxidase", because of its ability to reduce O 2 to water (albeit much more slowly than mammalian cytochrome c oxidase) and the presence of four electron acceptor groups per dimer. These studies were aimed at exploring the relationship between the bacterial and mammalian cytochrome oxidases.…”

Section: A Heme CD 1 -Containing Nitrite Reductasesmentioning

confidence: 99%