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rdf:type |
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lifeskim:mentions |
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pubmed:issue |
1
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pubmed:dateCreated |
2006-3-10
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pubmed:abstractText |
Homotetrameric MSDH (methylmalonate semialdehyde dehydrogenase) from Bacillus subtilis catalyses the NAD-dependent oxidation of MMSA (methylmalonate semialdehyde) and MSA (malonate semialdehyde) into PPCoA (propionyl-CoA) and acetyl-CoA respectively via a two-step mechanism. In the present study, a detailed mechanistic characterization of the MSDH-catalysed reaction has been carried out. The results suggest that NAD binding elicits a structural imprinting of the apoenzyme, which explains the marked lag-phase observed in the activity assay. The enzyme also exhibits a half-of-the-sites reactivity, with two subunits being active per tetramer. This result correlates well with the presence of two populations of catalytic Cys302 in both the apo- and holo-enzymes. Binding of NAD causes a decrease in reactivity of the two Cys302 residues belonging to the two active subunits and a pKapp shift from approx. 8.8 to 8.0. A study of the rate of acylation as a function of pH revealed a decrease in the pKapp of the two active Cys302 residues to approx. 5.5. Taken to-gether, these results support a sequential Cys302 activation process with a pKapp shift from approx. 8.8 in the apo-form to 8.0 in the binary complex and finally to approx. 5.5 in the ternary complex. The rate-limiting step is associated with the b-decarboxylation process which occurs on the thioacylenzyme intermediate after NADH release and before transthioesterification. These data also indicate that bicarbonate, the formation of which is enzyme-catalysed, is the end-product of the reaction.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-10388564,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-10504267,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-10727225,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-10864505,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-11009616,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-11412090,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-12196027,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-12764229,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-1339433,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-14504694,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-15272169,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-7034777,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-7819202,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-7873540,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-8439297,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-8444151,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-8527447,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-8615805,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-9095201,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-9195888,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-9219528,
http://linkedlifedata.com/resource/pubmed/commentcorrection/16332250-9226270
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/2,2'-Dipyridyl,
http://linkedlifedata.com/resource/pubmed/chemical/2,2'-dipyridyl disulfide,
http://linkedlifedata.com/resource/pubmed/chemical/Apoenzymes,
http://linkedlifedata.com/resource/pubmed/chemical/Bicarbonates,
http://linkedlifedata.com/resource/pubmed/chemical/Cysteine,
http://linkedlifedata.com/resource/pubmed/chemical/Disulfides,
http://linkedlifedata.com/resource/pubmed/chemical/Holoenzymes,
http://linkedlifedata.com/resource/pubmed/chemical/Iodoacetamide,
http://linkedlifedata.com/resource/pubmed/chemical/Methylmalonate-Semialdehyde...,
http://linkedlifedata.com/resource/pubmed/chemical/NAD
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pubmed:status |
MEDLINE
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pubmed:month |
Apr
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pubmed:issn |
1470-8728
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pubmed:author |
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pubmed:issnType |
Electronic
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pubmed:day |
1
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pubmed:volume |
395
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
107-15
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
pubmed-meshheading:16332250-2,2'-Dipyridyl,
pubmed-meshheading:16332250-Apoenzymes,
pubmed-meshheading:16332250-Bacillus subtilis,
pubmed-meshheading:16332250-Bicarbonates,
pubmed-meshheading:16332250-Catalysis,
pubmed-meshheading:16332250-Cysteine,
pubmed-meshheading:16332250-Decarboxylation,
pubmed-meshheading:16332250-Disulfides,
pubmed-meshheading:16332250-Holoenzymes,
pubmed-meshheading:16332250-Hydrogen-Ion Concentration,
pubmed-meshheading:16332250-Iodoacetamide,
pubmed-meshheading:16332250-Kinetics,
pubmed-meshheading:16332250-Methylmalonate-Semialdehyde Dehydrogenase (Acylating),
pubmed-meshheading:16332250-Mutation,
pubmed-meshheading:16332250-NAD,
pubmed-meshheading:16332250-Oxidation-Reduction,
pubmed-meshheading:16332250-Protein Binding,
pubmed-meshheading:16332250-Time Factors
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pubmed:year |
2006
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pubmed:articleTitle |
Mechanistic characterization of the MSDH (methylmalonate semialdehyde dehydrogenase) from Bacillus subtilis.
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pubmed:affiliation |
Maturation des ARN et Enzymologie Moléculaire, UMR 7567 CNRS-UHP, Université Henri Poincaré Nancy I, 54506 Vandoeuvre-lès-Nancy Cedex, France.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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