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