11087744

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Predicate	Object
rdf:type	pubmed:Citation
lifeskim:mentions	umls-concept:C0020275, umls-concept:C0041249, umls-concept:C0173022, umls-concept:C0311665, umls-concept:C0332479, umls-concept:C0443286, umls-concept:C1269765
pubmed:issue	9
pubmed:dateCreated	2001-3-6
pubmed:abstractText	C-H bond breakage by tryptophan tryptophylquinone (TTQ)-dependent methylamine dehydrogenase (MADH) occurs by vibrationally assisted tunneling (Basran, J., Sutcliffe, M. J., and Scrutton, N. S. (1999) Biochemistry 38, 3218--3222). We show here a similar mechanism in TTQ-dependent aromatic amine dehydrogenase (AADH). The rate of TTQ reduction by dopamine in AADH has a large, temperature independent kinetic isotope effect (KIE = 12.9 +/- 0.2), which is highly suggestive of vibrationally assisted tunneling. H-transfer is compromised with benzylamine as substrate and the KIE is deflated (4.8 +/- 0.2). The KIE is temperature-independent, but reaction rates are strongly dependent on temperature. With tryptamine as substrate reaction rates can be determined only at low temperature as C-H bond cleavage is rapid, and an exceptionally large KIE (54.7 +/- 1.0) is observed. Studies with deuterated tryptamine suggest vibrationally assisted tunneling is the mechanism of deuterium and, by inference, hydrogen transfer. Bond cleavage by MADH using a slow substrate (ethanolamine) occurs with an inflated KIE (14.7 +/- 0.2 at 25 degrees C). The KIE is temperature-dependent, consistent with differential tunneling of protium and deuterium. Our observations illustrate the different modes of H-transfer in MADH and AADH with fast and slow substrates and highlight the importance of barrier shape in determining reaction rate.
pubmed:language	eng
pubmed:journal	http://linkedlifedata.com/resource/pubmed/journal/2985121R
pubmed:citationSubset	IM
pubmed:chemical	http://linkedlifedata.com/resource/pubmed/chemical/Benzylamines, http://linkedlifedata.com/resource/pubmed/chemical/Ethanolamine, http://linkedlifedata.com/resource/pubmed/chemical/Indolequinones, http://linkedlifedata.com/resource/pubmed/chemical/Oxidoreductases Acting on CH-NH..., http://linkedlifedata.com/resource/pubmed/chemical/Quinones, http://linkedlifedata.com/resource/pubmed/chemical/Tryptamines, http://linkedlifedata.com/resource/pubmed/chemical/Tryptophan, http://linkedlifedata.com/resource/pubmed/chemical/aromatic amine dehydrogenase, http://linkedlifedata.com/resource/pubmed/chemical/benzylamine, http://linkedlifedata.com/resource/pubmed/chemical/methylamine dehydrogenase, http://linkedlifedata.com/resource/pubmed/chemical/tryptamine, http://linkedlifedata.com/resource/pubmed/chemical/tryptophan tryptophylquinone
pubmed:status	MEDLINE
pubmed:month	Mar
pubmed:issn	0021-9258
pubmed:author	pubmed-author:BasranJJ, pubmed-author:PatelSS, pubmed-author:ScruttonN SNS, pubmed-author:SutcliffeM JMJ
pubmed:issnType	Print
pubmed:day	2
pubmed:volume	276
pubmed:owner	NLM
pubmed:authorsComplete	Y
pubmed:pagination	6234-42
pubmed:dateRevised	2006-11-15
pubmed:meshHeading	pubmed-meshheading:11087744-Benzylamines, pubmed-meshheading:11087744-Catalysis, pubmed-meshheading:11087744-Ethanolamine, pubmed-meshheading:11087744-Indolequinones, pubmed-meshheading:11087744-Oxidoreductases Acting on CH-NH Group Donors, pubmed-meshheading:11087744-Quinones, pubmed-meshheading:11087744-Tryptamines, pubmed-meshheading:11087744-Tryptophan, pubmed-meshheading:11087744-Vibration
pubmed:year	2001
pubmed:articleTitle	Importance of barrier shape in enzyme-catalyzed reactions. Vibrationally assisted hydrogen tunneling in tryptophan tryptophylquinone-dependent amine dehydrogenases.
pubmed:affiliation	Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom.
pubmed:publicationType	Journal Article, Research Support, Non-U.S. Gov't