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Title: Structure of 6-diazo-5-oxo-norleucine-bound human gamma-glutamyl transpeptidase 1, a novel mechanism of inactivation

Intense efforts are underway to identify inhibitors of the enzyme gamma–glutamyl transpeptidase 1 (GGT1) which cleaves extracellular gamma–glutamyl compounds and contributes to the pathology of asthma, reperfusion injury and cancer. The glutamate analog, 6–diazo–5–oxo–norleucine (DON), inhibits GGT1. DON also inhibits many essential glutamine metabolizing enzymes rendering it too toxic for use in the clinic as a GGT1 inhibitor. We investigated the molecular mechanism of human GGT1 (hGGT1) inhibition by DON to determine possible strategies for increasing its specificity for hGGT1. DON is an irreversible inhibitor of hGGT1. The second order rate constant of inactivation was 0.052 m M –1 min –1 and the K i was 2.7 ± 0.7 m M. The crystal structure of DON–inactivated hGGT1 contained a molecule of DON without the diazo–nitrogen atoms in the active site. The overall structure of the hGGT1–DON complex resembled the structure of the apo–enzyme; however, shifts were detected in the loop forming the oxyanion hole and elements of the main chain that form the entrance to the active site. The structure of hGGT1–DON complex revealed two covalent bonds between the enzyme and inhibitor which were part of a six membered ring. The ring included the OG atom of Thr381, the reactivemore » nucleophile of hGGT1 and the α–amine of Thr381. As a result, the structure of DON–bound hGGT1 has led to the discovery of a new mechanism of inactivation by DON that differs from its inactivation of other glutamine metabolizing enzymes, and insight into the activation of the catalytic nucleophile that initiates the hGGT1 reaction.« less
 [1] ;  [2] ;  [3] ;  [1]
  1. Univ. of Oklahoma Health Sciences Center, Oklahoma City, OK (United States)
  2. Univ. of Oklahoma, Norman, OK (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0961-8368
Grant/Contract Number:
SC0012704; AC02-98CH10886; E-SC0012704
Accepted Manuscript
Journal Name:
Protein Science
Additional Journal Information:
Journal Volume: 26; Journal Issue: 6; Journal ID: ISSN 0961-8368
The Protein Society
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
36 MATERIALS SCIENCE; enzyme inactivation; enzyme kinetics; crystal structure; protein conformation; human gamma-glutamyl transpeptidase; gamma-glutamyl transferase
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1401773