Linked Life Data

8519766

Source:http://linkedlifedata.com/resource/pubmed/id/8519766

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
49
pubmed:dateCreated
1996-1-25
pubmed:abstractText
The dual-specificity phosphatases are unusual catalysts in that they can utilize protein substrates containing phosphotyrosine as well as phosphoserine/threonine. The dual-specificity phosphatases and the protein-tyrosine phosphatases (PTPases) share the active site motif (H/V)C(X)5R(S/T), but display little amino acid sequence identity outside of the active site. Although the dual-specificity phosphatases and the PTPases appear to bring about phosphate monoester hydrolysis through a similar mechanism, it is not clear what causes the difference in the active-site specificity between the two groups of enzymes. In this paper, we show that the human dual-specificity phosphatase, VHR [for VH1-Related; Ishibashi et al. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 12170-12174], is rather promiscuous toward small phosphate monoesters (including both aryl and alkyl phosphates of primary alcohols) with effectively identical kcat/Km and kcat values while the pKa values of the leaving groups (phenols or alcohols) varied from 7 to 16. Linear free-energy relationship analysis of kcat and kcat/Km of the enzyme-catalyzed hydrolysis reaction suggests that a uniform mechanism is utilized for both the aryl and alkyl substrates. The very small dependency of kcat/Km on the leaving group pKa can be accounted for by the protonation of the leaving group. Pre-steady-state burst kinetic analysis of the VHR-catalyzed hydrolysis of p-nitrophenyl phosphate provides direct kinetic evidence for the involvement of a phosphoenzyme intermediate in the dual specificity phosphatase-catalyzed reaction. The rate-limiting step for the VHR-catalyzed hydrolysis of p-nitrophenyl phosphate corresponds to the decomposition of the phosphoenzyme intermediate.(ABSTRACT TRUNCATED AT 250 WORDS)
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Dec
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
12
pubmed:volume
34
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
16088-96
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Transition state and rate-limiting step of the reaction catalyzed by the human dual-specificity phosphatase, VHR.
pubmed:affiliation
Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S.