Linked Life Data

7819238

Source:http://linkedlifedata.com/resource/pubmed/id/7819238

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1995-2-13
pubmed:abstractText
The oxyanion hole in cysteine and serine proteases can be viewed as an arrangement of prealigned dipoles that complements the changes in charge distribution during the enzymatic reaction. Because of the electrostatic nature of the interaction involved in the oxyanion hole, the introduction of charged residues in that region could have a major effect on the catalytic properties of the enzyme. In this study, residue Gln19, which contributes to one of the hydrogen bonds in the oxyanion hole of papain, has been replaced by glutamic acid, histidine, and asparagine residues. These mutations result in 65-315-fold decreases in kcat/KM, supporting our previous finding that the side chain of Gln19 contributes to transition state stabilization in the oxyanion hole of papain (Ménard et al., 1991a). Since papain is active over a wide range of pH values, the influence of side chain ionization on activity could be measured quantitatively with the mutant Gln19Glu. The pH dependency of kcat/KM for Gln19Glu is not of the classical bell-shaped form normally observed for papain, but instead is modulated by ionization of the Glu19 side chain with a pKa of 6.02. The Gln19Glu mutant at low pH, where the Glu19 side chain is neutral, is the enzyme that displays activity closest to that of wild-type enzyme, with a (kcat/KM)1lim value only 20-fold lower than that for papain. As expected, the activity of the Gln19Glu mutant decreases when the Glu19 side chain ionizes. However, introduction of the negatively charged glutamate into the oxyanion hole of papain leads to a further reduction in activity of only 12-fold, and this mutant is still more active than the Gln19Ser enzyme and only 3-fold less active than Gln19Asn.(ABSTRACT TRUNCATED AT 250 WORDS)
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
17
pubmed:volume
34
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
464-71
pubmed:dateRevised
2000-12-18
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Modification of the electrostatic environment is tolerated in the oxyanion hole of the cysteine protease papain.
pubmed:affiliation
Biotechnology Research Institute, National Research Council of Canada, Montréal, Québec.
pubmed:publicationType
Journal Article