Oxidoreductase required for tumor suppression. NAPDH-bound form inhibits nuclear import by competing with nuclear import substrates for binding to a subset of nuclear transport receptors. May act as a redox sensor linked to transcription through regulation of nuclear import. Isoform 1 is a metastasis suppressor with proapoptotic as well as antiangiogenic properties. Isoform 2 has an antiapoptotic effect.

Tissue specificity: Ubiquitous. Highest level in liver. High levels in lung, skeletal muscle, pancreas and placenta. Moderate levels in heart and kidney. Low levels in brain.