Serine/threonine phosphatase activity of calcineurin is inhibited by sodium orthovanadate and dithiothreitol reverses the inhibitory effect.
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.
Morioka
M
M
Department of Neurosurgery, Kumamoto University School of Medicine, Japan.
Fukunaga
K
K
Kawano
T
T
Hasegawa
S
S
Korematsu
K
K
Kai
Y
Y
Hamada
J
J
Miyamoto
E
E
Ushio
Y
Y
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D019703:Calcineurin / Q000378:metabolism; D065095:Calcineurin Inhibitors; D002417:Cattle; D004229:Dithiothreitol / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects / Q000201:enzymology; D008297:Male; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D012996:Solutions; D013997:Time Factors; D014638:Vanadates / Q000037:antagonists & inhibitors* / Q000494:pharmacology*
D065095:Calcineurin Inhibitors; D004791:Enzyme Inhibitors; D012996:Solutions; D014638:Vanadates; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D004229:Dithiothreitol