Intrinsic phosphatase activity of bovine brain calcineurin requires a tightly bound trace metal

The divalent metal requirement of intrinsic phosphatase activity was investigated using native and trypsinized calcineruin. This was assessed by examining (1) the stimulation of the enzyme by various metals, (2) the inhibition of the enzyme activity by metal chelators (EDTA and EGTA), and (3) the restoration by various metals of the activity of the EDTA-inhibited calcineurin phosphatase. The results supported the view that a tightly bound trace metal is necessary for expression of the phosphatase activity of calcineurin and implicate Mn 2+ as the tighly bound metal.