Linked Life Data

8917440

Source:http://linkedlifedata.com/resource/pubmed/id/8917440

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1997-1-9
pubmed:abstractText
Isoforms (1-4) of human tyrosine hydroxylase (TH) have been expressed in Escherichia coli and purified as apoenzymes (metal-free). Apo-human TH binds 1.0 atom Fe(II)/enzyme subunit, and iron binding is associated with an immediate and dramatic (40-fold) increase in specific activity. For X-ray absorption fine structure (XAFS) and electron paramagnetic resonance (EPR) measurements the apoenzyme was reconstituted with 56Fe and for Mössbauer measurements with 57Fe. XAFS measurements at the Fe-K edge of human TH were performed on the native form [Fe(II)-human TH], as well as after addition of stoichiometric amounts of the substrate tetrahydropterin, the inhibitor dopamine and of H2O2. The addition of dopamine or H2O2 oxidizes the ferrous iron of the native human TH to the ferric state. In both redox states the iron is octahedrally coordinated by low-Z backscatterers, thus sulfur coordination can be excluded. From the multiple scattering analysis of the EXAFS region is was surmised that part of the iron coordination is due to (3 +/- 1) imidazols. Addition of tetrahydropterin does not significantly change the iron coordination of the Fe(II) enzyme. The Mössbauer results confirm the valence states and the octahedral coordination of iron as well as the exclusion of sulfur ligation. Both the EPR spectra and the Mössbauer magnetic hyperfine pattern of dopamine- and H2O2-treated native human TH, were analyzed with the spin-Hamiltonian formalism. This analysis provides significantly different features for the two forms of human TH: the ferric iron (S = 5/2) of the H2O2-treated form exhibits a rhombic environment while that of the dopamine-treated form exhibits near-axial symmetry. The specific spectroscopic signature of dopamine-treated human TH, including that of an earlier resonance-Raman study [Michaud-Soret, I., Andersson, K. K., Que, L. Jr & Haavik, J. (1995) Biochemistry 34, 5504-5510] is most likely due to the bidentate binding of dopamine to iron.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
241
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
432-9
pubmed:dateRevised
2007-7-23
pubmed:meshHeading
pubmed:year
1996
pubmed:articleTitle
Mössbauer, electron-paramagnetic-resonance and X-ray-absorption fine-structure studies of the iron environment in recombinant human tyrosine hydroxylase.
pubmed:affiliation
Institut für Physik, Medizinische Universität zu Lübeck, Germany.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't