Linked Life Data

9492272

Source:http://linkedlifedata.com/resource/pubmed/id/9492272

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1-2
pubmed:dateCreated
1998-3-23
pubmed:abstractText
Copper amine oxidases utilize 2,4,5-trihydroxyphenylalanine quinone (topaquinone) as a cofactor in enzymatic catalysis. This cofactor is formed from a tyrosine residue through a self-catalytic mechanism with the participation of the copper ion at the active site. Although pathways have been postulated for topaquinone biogenesis, portions of this scheme are still unclear. We utilized 4-tert-butyl-derived models for the putative intermediates of topaquinone generation and studied the effect of Cu(II) and Zn(II) ions on each autoxidative step from dopa- to topaquinone-like compounds at physiological pH (7.4). Several polyvinyl-alcohol-based soluble resins bearing mono- and di-hydroxyphenolic moieties were also prepared, and their tendency to give hydroxyquinonic structures when incubated at alkaline pH values was investigated. Our results confirm (although indirectly) the formation of dopa and dopaquinone during topaquinone biosynthesis. Moreover, we collected evidence that, following the formation of dopa, the role of the active-site copper ion in topaquinone biogenesis would be limited to the catalysis of the two subsequent quinonization steps (i.e. from dopa to dopaquinone and from topa to topaquinone), thus disfavoring the possibility of a direct intervention of the metal ion in the hydroxylation of dopaquinone. In particular, Cu(II) was shown to influence deeply the autoxidation of 1,2,5-trihydroxy-4-tert-butylbenzene, used as model of topa, both increasing the reaction rate and changing its mechanism. The mechanistic implications of these findings for the biogenesis of topaquinone and its analogs at the active site of various amine oxidases are discussed.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
http://linkedlifedata.com/resource/pubmed/chemical/6-hydroxydopa quinone, http://linkedlifedata.com/resource/pubmed/chemical/Aldehydes, http://linkedlifedata.com/resource/pubmed/chemical/Amine Oxidase (Copper-Containing), http://linkedlifedata.com/resource/pubmed/chemical/Benzene Derivatives, http://linkedlifedata.com/resource/pubmed/chemical/Benzoquinones, http://linkedlifedata.com/resource/pubmed/chemical/Catalase, http://linkedlifedata.com/resource/pubmed/chemical/Catechols, http://linkedlifedata.com/resource/pubmed/chemical/Copper, http://linkedlifedata.com/resource/pubmed/chemical/Dihydroxyphenylalanine, http://linkedlifedata.com/resource/pubmed/chemical/Free Radical Scavengers, http://linkedlifedata.com/resource/pubmed/chemical/Superoxide Dismutase, http://linkedlifedata.com/resource/pubmed/chemical/Zinc, http://linkedlifedata.com/resource/pubmed/chemical/tert-butylbenzene, http://linkedlifedata.com/resource/pubmed/chemical/tert-butylcatechol
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
251
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
91-7
pubmed:dateRevised
2007-7-23
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Biosynthesis of the topaquinone cofactor in copper amine oxidases--evidence from model studies.
pubmed:affiliation
Istituto di Chimica Biologica, Università di Cagliari, Italy. rinaldi@vaxca1.unica.it
pubmed:publicationType
Journal Article