Linked Life Data

7759490

Source:http://linkedlifedata.com/resource/pubmed/id/7759490

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
21
pubmed:dateCreated
1995-6-28
pubmed:abstractText
Mutant human gamma-glutamyl transpeptidases with amino acid substitutions on the light subunit at the Asp residues conserved among several species, and at the unique cysteine residue (Cys-454), were prepared and expressed in a baculovirus insect cell system. Replacement of Asp-423 by Ala or Glu led to major loss of enzyme activity, consistent with the conclusion that Asp-423 is essential for activity. A mutant in which Cys-454 was replaced by Ala was fully active, indicating that the unique light subunit thiol is not required for catalysis. Kinetic analysis of the hydrolysis reaction of L-gamma-glutamyl-p-nitroanilide indicated that the decreased activity of Asp-423 mutants is the consequence of an extremely high substrate Km value, which is more than a 1000-fold greater than that for the wild-type enzyme, whereas the Vmax is decreased only less than 90-fold. The results suggest that Asp-423, and to a lesser extent Asp-422, interact electrostatically with the alpha-amino group of the gamma-glutamyl donor substrate. Although further studies are required to evaluate the possibility that the reaction involves function of a charge (or proton) relay system, the present work suggests that the gamma-glutamyl moiety of the substrate binds electrostatically to specific groups on the enzyme; this facilitates gamma-glutamyl enzyme formation.
pubmed:grant
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
26
pubmed:volume
270
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
12471-5
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Human gamma-glutamyl transpeptidase mutants involving conserved aspartate residues and the unique cysteine residue of the light subunit.
pubmed:affiliation
Department of Biochemistry, Cornell University Medical College, New York, New York 10021, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't