Linked Life Data

11695901

Source:http://linkedlifedata.com/resource/pubmed/id/11695901

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
45
pubmed:dateCreated
2001-11-6
pubmed:databankReference
pubmed:abstractText
Multisubstrate adduct inhibitors (MAI) of glycinamide ribonucleotide transformylase (GAR Tfase), which incorporate key features of the folate cofactor and the beta-GAR substrate, typically exhibit K(i)'s in the picomolar range. However, these compounds have reduced bioavailability due to the incorporation of a negatively charged phosphate moiety that prevents effective cellular uptake. Thus, a folate analogue that is capable of adduct formation with the substrate on the enzyme active site could lead to a potent GAR Tfase inhibitor that takes advantage of the cellular folate transport systems. We synthesized a dibromide folate analogue, 10-bromo-10-bromomethyl-5,8,10-trideazafolic acid, that was an intermediate designed to assemble with the substrate beta-GAR on the enzyme active site. We have now determined the crystal structure of the Escherichia coli GAR Tfase/MAI complex at 1.6 A resolution to ascertain the nature and mechanism of its time-dependent inhibition. The high-resolution crystal structure clearly revealed the existence of a covalent adduct between the substrate beta-GAR and the folate analogue (K(i) = 20 microM). However, the electron density map surprisingly indicated a C10 hydroxyl in the adduct rather than a bromide and suggested that the multisubstrate adduct is not formed directly from the dibromide but proceeds via an epoxide. Subsequently, we demonstrated the in situ conversion of the dibromide to the epoxide. Moreover, synthesis of the authentic epoxide confirmed that its inhibitory, time-dependent, and cytotoxic properties are comparable to those of the dibromide. Further, inhibition was strongest when the dibromide or epoxide is preincubated with both enzyme and substrate, indicating that inhibition occurs via the enzyme-dependent formation of the multisubstrate adduct. Thus, the crystal structure revealed the successful formation of an enzyme-assembled multisubstrate adduct and highlighted a potential application for epoxides, and perhaps aziridines, in the design of efficacious GAR Tfase inhibitors.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
13
pubmed:volume
40
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
13538-47
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
2001
pubmed:articleTitle
Unexpected formation of an epoxide-derived multisubstrate adduct inhibitor on the active site of GAR transformylase.
pubmed:affiliation
Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S.