Linked Life Data

10329670

Source:http://linkedlifedata.com/resource/pubmed/id/10329670

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
21
pubmed:dateCreated
1999-7-9
pubmed:abstractText
A kinetic analysis of MspI DNA methyltransferase (M.MspI) is presented. The enzyme catalyzes methylation of lambda-DNA, a 50-kilobase pair linear molecule with multiple M.MspI-specific sites, with a specificity constant (kcat/KM) of 0.9 x 10(8) M-1 s-1. But the values of the specificity constants for the smaller DNA substrates (121 and 1459 base pairs (bp)) with single methylation target or with multiple targets (sonicated lambda-DNA) were less by an order of magnitude. Product inhibition of the M.MspI-catalyzed methylation reaction by methylated DNA is competitive with respect to DNA and noncompetitive with respect to S-adenosylmethionine (AdoMet). The S-adenosylhomocysteine inhibition of the methylation reaction is competitive with respect to AdoMet and uncompetitive with respect to DNA. The presteady state kinetic analysis showed a burst of product formation when AdoMet was added to the enzyme preincubated with the substrate DNA. The burst is followed by a constant rate of product formation (0.06 mol per mol of enzyme s-1) which is similar to catalytic constants (kcat = approximately 0.056 s-1) measured under steady state conditions. The isotope exchange in chasing the labeled methyltransferase-DNA complex with unlabeled DNA and AdoMet leads to a reduced burst as compared with the one involving chase with labeled DNA and AdoMet. The enzyme is capable of exchanging tritium at C-5 of target cytosine in the substrate DNA in the absence of cofactor AdoMet. The kinetic data are consistent with an ordered Bi Bi mechanism for the M.MspI-catalyzed DNA methylation where DNA binds first.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
May
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
21
pubmed:volume
274
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
14743-9
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Kinetic mechanism of cytosine DNA methyltransferase MspI.
pubmed:affiliation
Department of Biochemical Engineering & Biotechnology, Indian Institute of Technology-Delhi, New Delhi 110016, India. sbhattac@pierre.hh.ri.ccf.org
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't