Linked Life Data

19570037

Source:http://linkedlifedata.com/resource/pubmed/id/19570037

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
2009-8-24
pubmed:abstractText
Substrate specificity is critically important for enzyme catalysis. In the adrenaline-synthesizing enzyme PNMT (phenylethanolamine N-methyltransferase), minor changes in substituents can convert substrates into inhibitors. Here we report the crystal structures of six human PNMT complexes, including the first structure of the enzyme in complex with its physiological ligand R-noradrenaline. Determining this structure required rapid soak methods because of the tendency for noradrenaline to oxidize. Comparison of the PNMT-noradrenaline complex with the previously determined PNMT-p-octopamine complex demonstrates that these two substrates form almost equivalent interactions with the enzyme and show that p-octopamine is a valid model substrate for PNMT. The crystal structures illustrate the adaptability of the PNMT substrate binding site in accepting multi-fused ring systems, such as substituted norbornene, as well as noradrenochrome, the oxidation product of noradrenaline. These results explain why only a subset of ligands recognized by PNMT are methylated by the enzyme; bulky substituents dictate the binding orientation of the ligand and can thereby place the acceptor amine too far from the donor methyl group for methylation to occur. We also show how the critical Glu(185) catalytic residue can be replaced by aspartic acid with a loss of only 10-fold in catalytic efficiency. This is because protein backbone movements place the Asp(185) carboxylate almost coincident with the carboxylate of Glu(185). Conversely, replacement of Glu(185) by glutamine reduces catalytic efficiency almost 300-fold, not only because of the loss of charge, but also because the variant residue does not adopt the same conformation as Glu(185).
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Sep
pubmed:issn
1470-8728
pubmed:author
pubmed:issnType
Electronic
pubmed:day
15
pubmed:volume
422
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
463-71
pubmed:meshHeading
pubmed:year
2009
pubmed:articleTitle
Molecular recognition of physiological substrate noradrenaline by the adrenaline-synthesizing enzyme PNMT and factors influencing its methyltransferase activity.
pubmed:affiliation
Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, The University of Queensland, Brisbane, Queensland 4072, Australia.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't, Research Support, N.I.H., Extramural