DUSP1 suppresses the activation of MAP kinase, Mitogen-activated protein kinase 1 for example, and specifies a protein with structural features similar to members of the non-receptor-type protein-tyrosine phosphorylases family.
Furthermore, it suppresses the activation of MAP kinase by oncogenic ras in extracts of Xenopus oocytes. The bacterially expressed and purified DUSP1 protein has intrinsic phosphatase activity, and specifically inactivates mitogen-activated protein (MAP) kinase in vitro by the concomitant dephosphorylation of both its phosphothreonine and phosphotyrosine residues. It specifies a protein with structural features similar to members of the non-receptor-type protein-tyrosine phosphatase family, and which has significant amino-acid sequence similarity to a Tyr/Ser-protein phosphatase encoded by the late gene H1 of vaccinia virus. 
