Linked Life Data

1249

Source:http://linkedlifedata.com/resource/pubmed/id/1249

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1976-3-18
pubmed:abstractText
1. The steady-state kinetics of the interconversion of CO2 and HCO3 catalyzed by human carbonic anhydrase C was studied using 1H2O and 2H2O as solvents. The pH-independent parts of the parameters k(cat) and Km are 3-4 times larger in 1H2O than in 2H2O for both directions of the reaction, while the ratios k(cat)/Km show much smaller isotope effects. With either CO2 or HCO3 as substrate the major pH dependence is observed in k(cat), while Km appears independent of pH. The pKa value characterizing the pH-rate profiles is approximately 0.5 unit larger in 2H2O than in 1H2O. 2. The hydrolysis of p-nitrophenyl acetate catalyzed by human carbonic anhudrase C is approximately 35% faster in 2H2O than in 1H2O. In both solvents the pKa values of the pH-rate profiles are similar to those observed for the CO2-HCO3 interconversion. 3. It is tentatively proposed that the rate-limiting step at saturating concentrations of CO2 or HCO3 is an intramolecular proton transfer between two ionizing groups in the active site. It cannot be decided whether the transformation between enzyme-bound CO2 and HCO3 involves a proton trnasfer or not.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
59
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
253-9
pubmed:dateRevised
2007-7-23
pubmed:meshHeading
pubmed:year
1975
pubmed:articleTitle
The catalytic mechanism of carbonic anhydrase. Hydrogen-isotope effects on the kinetic parameters of the human C isoenzyme.
pubmed:publicationType
Journal Article