FAD-dependent sulfhydryl oxidase that catalyzes the formation of disulfide bonds in viral proteins produced in the cell cytoplasm. O2 + 2 R'C(R)SH = H2O2 + R'C(R)S-S(R)CR' Interacts with A151R. Expressed the late phase of the replicative cycle. Belongs to the asfivirus B119L family.