Linked Life Data

7829493

Source:http://linkedlifedata.com/resource/pubmed/id/7829493

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1995-2-22
pubmed:abstractText
Cytochrome P450 purified from Fusarium oxysporum (P450nor) is a unique heme enzyme that catalyzes the reduction of nitric oxide to nitrous oxide with electrons directly transferred from NADH (2NO + NADH + H+--> N2O + H2O + NAD+). We studied the reaction of P450nor with NO and NADH using stopped-flow rapid scan and low temperature spectroscopic methods. The NO ligand can bind to the ferric enzyme to form the stable NO bound complex, P450nor(Fe3+NO). Reduction of P450nor(Fe3+NO) with NADH yielded an intermediate, which transiently formed (tau = approximately 100 ms) and spontaneously decomposed to the Fe3+ state. The optical absorption spectrum of the intermediate was different from that of P450nor(Fe2+NO), which was formed by either a one-electron reduction of P450nor(Fe3+NO) with Na2S2O4 or NO binding to P450nor(Fe2+). On the basis of these observations, we suggested that the intermediate is presumably a two-electron reduced product of P450nor(Fe3+NO) by NADH, formally the (Fe3+NO)2-complex. We determined the rate constants of these reactions at 10 degrees C for the NO binding to P450nor(Fe3+) (2.6 x 10(7) M-1 s-1), the NADH reduction of P450nor(Fe3+NO) (0.9 x 10(6) M-1 s-1), and the spontaneous decomposition of the intermediate (0.027 s-1). In these kinetic measurements, it was found that the former two processes are fast enough, while the latter is extremely slow, compared with the fast turnover of the catalytic reaction (1200 s-1 at 10 degrees C), which we measured by monitoring the NADH consumption. Therefore, we suggested that in the catalytic cycle, decomposition of the intermediate is fairly accelerated by free NO, resulting in such a fast turnover. On the basis of several lines of the spectroscopic and the kinetic evidence, we proposed a possible mechanism of the NO reduction by P450nor.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
27
pubmed:volume
270
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1617-23
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Spectroscopic and kinetic studies on reaction of cytochrome P450nor with nitric oxide. Implication for its nitric oxide reduction mechanism.
pubmed:affiliation
Institute of Physical and Chemical Research (RIKEN), Saitama, Japan.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, Non-U.S. Gov't