cDNA‐directed expression of human thyroid peroxidase

Abstract

A human thyroid peroxidase cDNA, hTPO-1 [(1987) Proc. Natl. Acad. Sci. USA 84, 5555-5559], was expressed in human Hep G2 cells using a vaccinia virus cDNA-expression system. When examined by immunoblot analysis, the level of hTPO-1 protein expression reached a maximum approx. 24 h after infection and remained at a similar level up to 72 h post-infection. The expressed protein was enzymatically active as measured by guaiacol oxidation. Monoclonal antibody-assisted immunoaffinity column chromatography was used for partial purification of vaccinia-expressed hTPO-1, resulting in more than 300-fold higher specific activity and a measurable difference spectrum of the hTPO-1 (Fe3+)-CN complex.