Abstract
Reactive oxygen species (ROS) generate oxidative damage to DNA and cause mutation. 8-oxoG, an oxidative form of guanine, pairs with adenine as well as cytosine. 8-oxodGTP is incorporated opposite adenine on template DNA as well as cytosine during DNA replication inducing A:T to C:G. base substitution if not the mismatch repaired.
MutT (8-oxodGTP pyrophosphohydrolase, 8-oxodGTPase) prevents an incorporation of the 8-oxoG by hydrolysis of 8-oxodGTP to 8-oxo-dGMP in E. coli. MutT system should be an essential function to suppress mutation because E. coli strain without such genes is quite highly mutable. Functional homolog of MutT has been found in human, mouse and rat (MTH1) and Arabidopsis (AtNUD1). We investigated 8-oxodGTPase activity in C. elegans. Crude extracts from C. elegans hydrolysed 8-oxodGTP to 8-oxo-dGMP. Purification of the extracts was carried out by salting-out, ultrafiltration, ion exchange and heparin chromatography. Partially purified enzyme contained the activity to hydrolyze 8-oxodGTP to 8-oxo-dGMP . Mg2+ ion was required for the activity and an optimum pH was in alkaline regions. The preparation hydrolyzed 2-OHdATP to 2-OHdAMP and did not dATP and dGTP. The enzyme was suggested to be the MTH1 type in mammalian cells.
