Carcinogenesis, Vol 19, 911-917, Copyright © 1998 by Oxford University Press
VM Lakshmi, TV Zenser and BB Davis
N'-(3'-Monophospho-deoxyguanosin-8-yl)-N-acetylbenzidine (dGp-ABZ) is
thought to play an important role in initiation of benzidine-induced
bladder cancer in humans. This report assesses the possible formation of
this adduct by peroxidatic activation of N-acetylbenzidine (ABZ). Adduct
formation was measured by 32P-post-labeling. Ram seminal vesicle microsomes
were used as a source of prostaglandin H synthase (PHS). The peroxidatic
activity of PHS was compared with that for horseradish peroxidase. Both
peroxidases converted ABZ to dGp-ABZ whether DNA or 2'- deoxyguanosine
3'-monophosphate (dGp) was present. Following 32P-post- labeling, the
enzymatic and synthetic adduct were extracted from PEI- cellulose plates
and were shown to have the same HPLC elution profiles for the bisphosphate
adduct (32P-dpGp-ABZ). Treatment of the enzymatic and synthetic
bisphosphate adduct with nuclease P1 yielded a product that eluted at the
same time from the HPLC (32P-dpG-ABZ). Additional experiments demonstrated
that the PHS-derived 5'-monophosphate (dpG- ABZ) and 3'-monophosphate
(dGp-ABZ) adducts were also identical to their corresponding synthetic
standard. With comparable amounts of total ABZ metabolism, PHS produced
approximately 40-fold more dGp-ABZ than horseradish peroxidase (1943 +/-
339 versus 49 +/- 7.8 fmol/mg dGp). Adduct formation was dependent upon the
presence of peroxidase and the specific substrate, i.e. arachidonic acid or
H2O2. Adduct formation by PHS was inhibited by indomethacin (0.1 mM),
ascorbic acid (1 mM) and glutathione (10 mM), but not by
5,5-dimethyl-1-pyrroline N- oxide (DMPO) (100 mM), a radical scavenger.
Horseradish peroxidase adduct formation was also inhibited by ascorbic acid
and glutathione. In addition, DMPO elicited greater than a 96% inhibition.
Results demonstrate peroxidatic metabolism of ABZ to form dGp-ABZ. The
mechanism of dGp-ABZ formation by PHS and horseradish peroxidase may be
different.
ARTICLES
N'-(3'-monophospho-deoxyguanosin-8-yl)-N-acetylbenzidine formation by peroxidative metabolism
VA Medical Center and Department of Biochemistry, St Louis University School of Medicine, MO 63125, USA.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  V. M. Lakshmi, F. F. Hsu, A. E. McGarry, B. B. Davis, and T. V. Zenser Hypochlorous Acid-Mediated Activation of N-acetylbenzidine to Form N'-(3'-monophospho-deoxyguanosin-8-yl)-N-acetylbenzidine Toxicol. Sci., February 1, 2000; 53(2): 202 - 212. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Ciotti, V. M. Lakshmi, N. Basu, B. B. Davis, I. S. Owens, and T. V. Zenser Glucuronidation of benzidine and its metabolites by cDNA-expressed human UDP-glucuronosyltransferases and pH stability of glucuronides Carcinogenesis, October 1, 1999; 20(10): 1963 - 1969. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. V. Zenser, V. M. Lakshmi, and B. B. Davis Human and Escherichia coli beta -Glucuronidase Hydrolysis of Glucuronide Conjugates of Benzidine and 4-Aminobiphenyl, and their Hydroxy Metabolites Drug Metab. Dispos., September 1, 1999; 27(9): 1064 - 1067. [Abstract] [Full Text]
|
|
|
|
 |
|
 T. V. Zenser, V. M. Lakshmi, F. F. Hsu, and B. B. Davis Peroxygenase Metabolism of N-Acetylbenzidine by Prostaglandin H Synthase. FORMATION OF AN N-HYDROXYLAMINE J. Biol. Chem., May 21, 1999; 274(21): 14850 - 14856. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. V. Zenser, V. M. Lakshmi, and B. B. Davis N-Glucuronidation of Benzidine and Its Metabolites. Role in Bladder Cancer Drug Metab. Dispos., September 1, 1998; 26(9): 856 - 859. [Abstract] [Full Text]
|
|