Orf virus encodes a functional dUTPase gene

The present study is the first report on the functional activity of a parapoxvirus-encoded dUTPase. The dUTPase gene of the attenuated orf virus (ORFV), strain D1701, was expressed as a bacterial thioredoxin fusion protein. In vitro assays showed that ORFV dUTPase was highly specific for dUTP as substrate. The enzyme was active over a broad pH range (pH 6.0-9.0), with maximal enzymatic activity at pH 7.0 in the presence of Mg2+ cations. Kinetic studies of the recombinant ORFV dUTPase revealed an apparent K-m of 4.0 muM, which is more similar to that of the mammalian or African swine fever virus enzyme than to the K-m of vaccinia virus dUTPase. Enzyme activity was also found with purified ORFV particles, indicating its virion association.