期刊
ANALYTICAL BIOCHEMISTRY
卷 416, 期 1, 页码 112-116出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ab.2011.05.008
关键词
DNA repair; Enzyme assay; Kinetics; TDP2; High-throughput screening
资金
- American Cancer Society [IRG-92-152-17]
- National Institutes of Health [RO1 CA 92306]
Tyrosyl DNA phosphodiesterase 2 (TDP2), a newly discovered enzyme that cleaves 5'-phosphotyrosyl bonds, is a potential target for chemotherapy. TDP2 possesses both 3'- and 5'-tyrosyl-DNA phosphodiesterase activity, which is generally measured in a gel-based assay using 3'- and 5'-phosphotyrosyl linkage at the 3' and 5' ends of an oligonucleotide. To understand the enzymatic mechanism of this novel enzyme, the gel-based assay is useful, but this technique is cumbersome for TDP2 inhibitor screening. For this reason, we have designed a novel assay using p-nitrophenyl-thymidine-5'-phosphate (T5PNP) as a substrate. This assay can be used in continuous colorimetric assays in a 96-well format. We compared the salt and pH effect on product formation with the colorimetric and gel-based assays and showed that they behave similarly. Steady-state kinetic studies showed that the 5' activity of TDP2 is 1000-fold more efficient than T5PNP. Tyrosyl DNA phosphodiesterase 1 (TDP1) and human AP-endonuclease 1 (APE1) could not hydrolyze T5PNP. Sodium orthovanadate, a known inhibitor of TDP2, inhibits product formation from T5PNP by TDP2 (IC50 = 40 mM). Our results suggest that this novel assay system with this new TDP2 substrate can be used for inhibitor screening in a high-throughput manner. (C) 2011 Elsevier Inc. All rights reserved.
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