Linked Life Data

9783167

Source:http://linkedlifedata.com/resource/pubmed/id/9783167

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1998-12-30
pubmed:abstractText
Mesophilic nitrile-degrading enzymes are widely dispersed in the Bacteria and lower orders of the eukaryotic kingdom. Two distinct enzyme systems, a nitrilase catalyzing the direct conversion of nitriles to carboxylic acids and separate but cotranscribed nitrile hydratase and amidase activities, are now well known. Nitrile hydratases are metalloenzymes, incorporating FeIII or CoII ions in thiolate ligand networks where they function as Lewis acids. In comparison, nitrilases are thiol-enzymes and the two enzyme groups have little or no apparent sequence or structural homology. The hydratases typically exist as alpha beta dimers or tetramers in which the alpha- and beta-subunits are similar in size but otherwise unrelated. Nitrilases however, are usually found as homomultimers with as many as 16 subunits. Until recently, the two nitrile-degrading enzyme classes were clearly separated by functional differences, the nitrile hydratases being aliphatic substrate specific and lacking stereoselectivity, whereas the nitrilases are enantioselective and aromatic substrate specific. The recent discovery of novel enzymes in both classes (including thermophilic representatives) has blurred these functional distinctions. Purified mesophilic nitrile-degrading enzymes are typically thermolabile in buffered solution, rarely withstanding exposure to temperatures above 50 degrees C without rapid inactivation. However, operational thermostability is often increased by addition of aliphatic acids or by use of immobilized whole cells. Low molecular stability has frequently been cited as a reason for the limited industrial application of "nitrilases"; such statements notwithstanding, these enzymes have been successfully applied for more than a decade to the kiloton production of acrylamide and more recently to the smaller-scale production of nicotinic acid, R-(-)-mandelic acid and S-(+)-ibuprofen. There is also a rapidly growing catalog of other potentially useful conversions of complex nitriles in which the regioselectivity of the enzyme coupled with the ability to achieve high conversion efficiencies without detriment to other sensitive functionalities is a distinct process advantage.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
1431-0651
pubmed:author
pubmed:issnType
Print
pubmed:volume
2
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
207-16
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Biochemistry and biotechnology of mesophilic and thermophilic nitrile metabolizing enzymes.
pubmed:affiliation
Department of Biochemistry and Molecular Biology, University College London, U.K. don.cowan@ucl.ac.uk
pubmed:publicationType
Journal Article, Review