Linked Life Data

12909646

Source:http://linkedlifedata.com/resource/pubmed/id/12909646

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
42
pubmed:dateCreated
2003-10-13
pubmed:abstractText
Experiments on cryptically chiral ethanes have indicated that the particulate methane monooxygenase (pMMO) from Methylococcus capsulatus (Bath) catalyzes the hydroxylation of ethane with total retention of configuration at the carbon center attacked. This result would seem to rule out a radical mechanism for the hydroxylation chemistry, at least as mediated by this enzyme. The interpretation of subsequent experiments on n-propane, n-butane, and n-pentane has been complicated by hydroxylation at both the pro-R and pro-S secondary C-H bonds, where the hydroxylation takes place. It has been suggested that these results merely reflect presentation of both the pro-R and pro-S C-H bonds to the hot "oxygen atom" species generated at the active site, and that the oxo-transfer chemistry, in fact, proceeds concertedly with retention of configuration. In the present work, we have augmented these earlier studies with experiments on [2,2-2H2]butane and designed d,l form chiral dideuteriobutanes. Essentially equal amounts of (2R)-[3,3-2H2]butan-2-ol and (2R)-[2-2H1]butan-2-ol are produced upon hydroxylation of [2,2-2H2]butane. The chemistry is stereospecific with full retention of configuration at the secondary carbon oxidized. In the case of the various chiral deuterated butanes, the extent of configurational inversion has been shown to be negligible for all the chiral butanes examined. Thus, the hydroxylation of butane takes place with full retention of configuration in butane as well as in the case of ethane. These results are interpreted in terms of an oxo-transfer mechanism based on side-on singlet oxene insertion across the C-H bond similar to that previously noted for singlet carbene insertion (Kirmse, W., and Ozkir, I. S. (1992) J. Am. Chem. Soc. 114, 7590-7591). Finally, we discuss how even the oxene insertion mechanism, with "spin crossover" in the transition state, could lead to small amounts of radical rearrangement products, if and when such products are observed. A scheme is described that unifies the two extreme mechanistic limits, namely the concerted oxene insertion and the hydrogen abstraction radical rebound mechanism within the same over-arching framework.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
17
pubmed:volume
278
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
40658-69
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2003
pubmed:articleTitle
The stereospecific hydroxylation of [2,2-2H2]butane and chiral dideuteriobutanes by the particulate methane monooxygenase from Methylococcus capsulatus (Bath).
pubmed:affiliation
Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't