Enzymatic catabolism of the mutagenic DNA precursor, 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP), in rainbow trout liver.

Authors

Karol Bialkowski, Tomasz Gnatowski

Published in

Fish physiology and biochemistry. Volume 52. Issue 4. Jul 01, 2026. Epub Jul 01, 2026.

Abstract

We characterized the catabolic pathway of 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP) in the liver of rainbow trout (a representative of lower vertebrates) and determined the specific levels of all involved enzymatic activities. We analyzed the time-course kinetics of enzymatic hydrolysis of 40 µM 8-oxo-dGTP, 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-diphosphate (8-oxo-dGDP), and 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-monophosphate (8-oxo-dGMP) by an extract of rainbow trout liver at pH 8.5 and 5.5. Four different enzymatic activities were found to participate in decomposition of 8-oxo-dGTP to a final product 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG), i.e., 8-oxo-dGTP pyrophosphohydrolase (specific activity at pH 8.5 107 U/mg protein, inactive at pH 5.5), 8-oxo-dGTP monophosphohydrolase (105 U/mg protein at pH 8.5, 181 U/mg protein at pH 5.5), 8-oxo-dGDP monophosphohydrolase (56 U/mg protein at pH 8.5, 188 U/mg protein at pH 5.5), and 8-oxo-dGMP phosphohydrolase (178 U/mg protein at pH 8.5, 485 U/mg protein at pH 5.5). At pH 8.5, all four enzymatic activities appeared to be dependent on magnesium ions (5 mM), as they were inhibited by 12.5 mM divalent metal ion chelator, ethylenediaminetetraacetic acid (EDTA). However, EDTA did not inhibit any of the three enzymatic activities detected at pH 5.5. There are two possible explanations for this phenomenon. The chelating power of EDTA in an acidic environment may be too low to remove Mg²⁺ ions from the active sites of enzymes, or these reactions are catalyzed by a completely different set of magnesium-independent enzymes that exhibit an acidic pH optimum characteristic of lysosomal enzymes. A thirty-kilo Dalton ultrafiltrate of the liver extract contained exclusively Mg²⁺-dependent 8-oxo-dGTP pyrophosphohydrolase (207 U/mg protein) and very low 8-oxo-dGDP monophosphohydrolase (5 U/mg protein) activities at pH 8.5. This indicates that trout 8-oxo-dGTP pyrophosphohydrolase has features that are closer to mammalian MTH1 (NUDT1) enzymes than bacterial MutT proteins, which efficiently decompose both 8-oxo-dGTP and 8-oxo-dGDP.

PMID:
42380525
Bibliographic data and abstract were imported from PubMed on 15 Aug 2026.

Read full publication at:
Please sign in to see all details.

Stats

1-terrible, 9-excellent. How would you rate this publication? Sign in in to submit your rating.

Post a comment

You need to be signed in to post comments. You can sign in here.

Comments

There are no comments yet.