PMID- 11511177
OWN - NLM
STAT- MEDLINE
DCOM- 20011101
LR  - 20190921
IS  - 0893-228X (Print)
IS  - 0893-228X (Linking)
VI  - 14
IP  - 8
DP  - 2001 Aug
TI  - Interaction of gamma-glutamyltranspeptidase with clofibryl-S-acyl-glutathione in 
      vitro and in vivo in rat.
PG  - 1033-40
AB  - Clofibric acid (CA) is metabolized to chemically reactive acylating products that 
      can transacylate glutathione to form clofibryl-S-acyl-glutathione (CA-SG) in 
      vitro and in vivo. We investigated the first step in the degradation of CA-SG to 
      the mercapturic acid conjugate, clofibryl-S-acyl-N-acetylcysteine (CA-SNAC), 
      which is catalyzed by gamma-glutamyltranspeptidase (gamma-GT). After gamma-GT 
      mediated cleavage of glutamate from CA-SG, the product 
      clofibryl-S-acyl-cysteinylglycine (CA-S-CG) should undergo an intramolecular 
      rearrangement reaction [Tate, S. S. (1975) FEBS Lett. 54, 319-322] to form 
      clofibryl-N-acyl-cysteinylglycine (CA-N-CG). We performed in vitro studies 
      incubating CA-SG with gamma-GT to determine the products formed, and in vivo 
      studies examining the products excreted in urine after dosing rats with CA-SG or 
      CA. Thus, CA-SG (0.1 mM) was incubated with gamma-GT (0.1 unit/mL) in buffer (pH 
      7.4, 25 degrees C) and analyzed for products formed by reversed-phase HPLC and 
      electrospray mass spectrometry (ESI/MS). Results showed that CA-SG is degraded 
      completely after 6 h of incubation leading to the formation of two products, 
      CA-N-CG and its disulfide, with no detection of CA-S-CG thioester. After 36 h of 
      incubation, only the disulfide remained in the incubation. Treatment of the 
      disulfide with dithiothreitol led to the reappearance of CA-N-CG. ESI/LC/MS 
      analysis of urine (16 h) extracts of CA-SG-dosed rats (200 mg/kg, iv) showed that 
      CA-SG is degraded to CA-N-CG, CA-N-acyl-cysteine (CA-N-C) and their respective 
      S-methylated products. The mercapturic acid conjugate (CA-SNAC) was found as a 
      minor product. Analysis of urine extracts from CA-dosed rats (200 mg/kg, ip) 
      resulted in the detection of clofibryl-N-acyl-cysteine (CA-N-C), but no evidence 
      for the formation of CA-SNAC was obtained. These in vitro and in vivo experiments 
      indicate that gamma-GT mediated degradation of clofibryl-S-acyl-glutathione leads 
      primarily to the formation and excretion of clofibryl-N-acyl-cysteine products 
      rather than the S-acyl-NAC conjugate.
FAU - Grillo, M P
AU  - Grillo MP
AD  - Department of Biopharmaceutical Sciences, University of California, San 
      Francisco, CA 94143-0446, USA.
FAU - Benet, L Z
AU  - Benet LZ
LA  - eng
GR  - GM36633/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - Chem Res Toxicol
JT  - Chemical research in toxicology
JID - 8807448
RN  - 0 (Anticholesteremic Agents)
RN  - 0 (clofibryl-acyl-glutathione)
RN  - 53PF01Q249 (Clofibric Acid)
RN  - EC 2.3.2.2 (gamma-Glutamyltransferase)
RN  - GAN16C9B8O (Glutathione)
SB  - IM
MH  - Acylation
MH  - Animals
MH  - Anticholesteremic Agents/*chemistry/pharmacokinetics
MH  - Chromatography, High Pressure Liquid
MH  - Clofibric Acid/*chemistry/pharmacokinetics
MH  - Glutathione/analogs & derivatives/*chemistry
MH  - Kinetics
MH  - Male
MH  - Mass Spectrometry
MH  - Rats
MH  - Rats, Sprague-Dawley
MH  - gamma-Glutamyltransferase/*metabolism
EDAT- 2001/08/21 10:00
MHDA- 2001/11/03 10:01
CRDT- 2001/08/21 10:00
PHST- 2001/08/21 10:00 [pubmed]
PHST- 2001/11/03 10:01 [medline]
PHST- 2001/08/21 10:00 [entrez]
AID - tx010039x [pii]
AID - 10.1021/tx010039x [doi]
PST - ppublish
SO  - Chem Res Toxicol. 2001 Aug;14(8):1033-40. doi: 10.1021/tx010039x.