Orthovanadate is known to be an inhibitor of protein tyrosine phosphatases. However, we found that it inhibited calcineurin which has the activity of a serine/threonine protein phosphatase, using casein phosphorylated by cyclic AMP-dependent protein kinase as a substrate. Orthovanadate inhibits the Mn2+-activated activity of purified calcineurin to 20%; this is not the case without Mn2+. Furthermore, 10 mM dithiothreitol (DTT) reversed the inhibitory effects of orthovanadate. Orthovanadate showed the same inhibitory effect for calcineurin activity in homogenates as for the purified enzyme; the inhibitory effect was reversed by DTT. These results indicate that orthovanadate inhibits not only protein tyrosine phosphatases as reported, but also serine/threonine phosphatase activity of calcineurin.
|Number of pages||4|
|Journal||Biochemical and biophysical research communications|
|Publication status||Published - 1998 Dec 18|
- Sodium orthovanadate
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology