Linked Life Data

1735441

Source:http://linkedlifedata.com/resource/pubmed/id/1735441

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1992-3-11
pubmed:abstractText
Aspartate aminotransferase (mitochondrial isoenzyme from chicken) has been found to racemize very slowly dicarboxylic amino acid substrates in the presence of their cognate oxo acids [Kochhar, S. & Christen, P. (1988) Eur. J. Biochem. 175, 433-438]. Tyrosine, phenylalanine and alanine are racemized at the same rate although they undergo the transamination reaction 3-5 orders of magnitude more slowly than the dicarboxylic substrates. Similarly, the truncated enzyme aspartate aminotransferase-(27/32-410) catalyzes the racemization at the same rate as the native enzyme, while its rate of transamination is decreased to 3% of that of the native enzyme. Apparently, the rate-limiting step in racemization is not immediately linked to the transamination cycle. Decreasing the water concentration in the reaction medium by adding methanol at 0 degrees C drastically reduces the rate of racemization without affecting the rate of transamination. On the basis of these and additional kinetic data and the model of the three-dimensional structure of the active site, we conclude that a water molecule is responsible for the protonation of C alpha of the coenzyme-substrate intermediate from the wrong side. The diffusion of the water molecule into the interior of the enzyme appears to be the rate-limiting step in aspartate-aminotransferase-catalyzed racemization.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Feb
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
203
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
563-9
pubmed:dateRevised
2007-7-23
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Mechanism of racemization of amino acids by aspartate aminotransferase.
pubmed:affiliation
Biochemisches Institut, Universität Zürich, Switzerland.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't