PMID- 19478237
OWN - NLM
STAT- MEDLINE
DCOM- 20090917
LR  - 20171116
IS  - 1096-0929 (Electronic)
IS  - 1096-0929 (Linking)
VI  - 110
IP  - 2
DP  - 2009 Aug
TI  - Mechanism of thiol-supported arsenate reduction mediated by 
      phosphorolytic-arsenolytic enzymes: II. Enzymatic formation of arsenylated 
      products susceptible for reduction to arsenite by thiols.
PG  - 282-92
LID - 10.1093/toxsci/kfp113 [doi]
AB  - Enzymes catalyzing the phosphorolytic cleavage of their substrates can reduce 
      arsenate (AsV) to the more toxic arsenite (AsIII) via the arsenolytic substrate 
      cleavage in presence of a reductant, as glutathione or dithiotreitol (DTT). We 
      have shown this for purine nucleoside phosphorylase (PNP), 
      glyceraldehyde-3-phosphate dehydrogenase (GAPDH), glycogen phosphorylase-a (GPa), 
      and phosphotransacetylase (PTA). Using a multidisciplinary approach, we explored 
      the mechanism whereby these enzymes mediate AsV reduction. It is known that PNP 
      cleaves inosine with AsV into hypoxanthine and ribose-1-arsenate. In presence of 
      inosine, AsV and DTT, PNP mediates AsIII formation. In this study, we incubated 
      PNP first with inosine and AsV, allowing the arsenolytic reaction to run, then 
      blocked this reaction with the PNP inhibitor BCX-1777, added DTT and continued 
      the incubation. Despite inhibition of PNP, large amount of AsIII was formed in 
      these incubations, indicating that PNP does not reduce AsV directly but forms a 
      product (i.e., ribose-1-arsenate) that is reduced to AsIII by DTT. Similar 
      studies with the other arsenolytic enzymes (GPa, GAPDH, and PTA) yielded similar 
      results. Various thiols that differentially supported AsV reduction when present 
      during PNP-catalyzed arsenolysis (DTT approximately dimercaptopropane-1-sulfonic 
      acid > mercaptoethanol > DMSA > GSH) similarly supported AsV reduction when added 
      only after a transient PNP-catalyzed arsenolysis, which preformed 
      ribose-1-arsenate. Experiments with progressively delayed addition of DTT after 
      BCX-1777 indicated that ribose-1-arsenate is short-lived with a half-life of 4 
      min. In conclusion, phosphorolytic enzymes, such as PNP, GAPDH, GPa, and PTA, 
      promote thiol-dependent AsV reduction because they convert AsV into arsenylated 
      products reducible by thiols more readily than AsV. In support of this view, 
      reactivity studies using conceptual density functional theory reactivity 
      descriptors (local softness, nucleofugality) indicate that reduction by thiols of 
      the arsenylated metabolites is favored over AsV.
FAU - Gregus, Zoltan
AU  - Gregus Z
AD  - Department of Pharmacology and Pharmacotherapy, Toxicology Section, University of 
      Pecs, Medical School, Pecs 7624, Hungary. zoltan.gregus@aok.pte.hu
FAU - Roos, Goedele
AU  - Roos G
FAU - Geerlings, Paul
AU  - Geerlings P
FAU - Nemeti, Balazs
AU  - Nemeti B
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20090528
PL  - United States
TA  - Toxicol Sci
JT  - Toxicological sciences : an official journal of the Society of Toxicology
JID - 9805461
RN  - 0 (Arsenates)
RN  - 0 (Arsenites)
RN  - 0 (Bacterial Proteins)
RN  - 0 (Enzyme Inhibitors)
RN  - 0 (Purine Nucleosides)
RN  - 0 (Pyrimidinones)
RN  - 0 (Sodium Compounds)
RN  - 0 (Sulfhydryl Compounds)
RN  - 4076-02-2 (Unithiol)
RN  - 426X066ELK (forodesine)
RN  - 48OVY2OC72 (sodium arsenite)
RN  - 5A614L51CT (Inosine)
RN  - 60-24-2 (Mercaptoethanol)
RN  - 72-89-9 (Acetyl Coenzyme A)
RN  - 7XO134LHLN (sodium arsenate)
RN  - DX1U2629QE (Succimer)
RN  - EC 1.2.1.- (Glyceraldehyde-3-Phosphate Dehydrogenases)
RN  - EC 2.3.1.8 (Phosphate Acetyltransferase)
RN  - EC 2.4.1.- (Glycogen Phosphorylase)
RN  - EC 2.4.2.1 (Purine-Nucleoside Phosphorylase)
RN  - GAN16C9B8O (Glutathione)
RN  - T8ID5YZU6Y (Dithiothreitol)
SB  - IM
MH  - Acetyl Coenzyme A/metabolism
MH  - Animals
MH  - Arsenates/*metabolism
MH  - Arsenites/*metabolism
MH  - Bacterial Proteins/*metabolism
MH  - Cattle
MH  - Dithiothreitol/metabolism
MH  - Enzyme Inhibitors/pharmacology
MH  - Glutathione/metabolism
MH  - Glyceraldehyde-3-Phosphate Dehydrogenases/*metabolism
MH  - Glycogen Phosphorylase/*metabolism
MH  - Half-Life
MH  - Inosine/metabolism
MH  - Kinetics
MH  - Mercaptoethanol/metabolism
MH  - Models, Chemical
MH  - Oxidation-Reduction
MH  - Phosphate Acetyltransferase/*metabolism
MH  - Purine Nucleosides/pharmacology
MH  - Purine-Nucleoside Phosphorylase/antagonists & inhibitors/*metabolism
MH  - Pyrimidinones/pharmacology
MH  - Rabbits
MH  - Sodium Compounds/*metabolism
MH  - Succimer/metabolism
MH  - Sulfhydryl Compounds/*metabolism
MH  - Unithiol/metabolism
EDAT- 2009/05/30 09:00
MHDA- 2009/09/18 06:00
CRDT- 2009/05/30 09:00
PHST- 2009/05/30 09:00 [entrez]
PHST- 2009/05/30 09:00 [pubmed]
PHST- 2009/09/18 06:00 [medline]
AID - kfp113 [pii]
AID - 10.1093/toxsci/kfp113 [doi]
PST - ppublish
SO  - Toxicol Sci. 2009 Aug;110(2):282-92. doi: 10.1093/toxsci/kfp113. Epub 2009 May 
      28.