Dephosporylation with alkaline phosphatase of histone and fibrinogen phosphorylated with protein kinase C in vitro.

Alkaline phosphatase from calf intestinal mucosa dephosphorylated histone H1 and fibrinogen that had been phosphorylated with protein kinase C. The reaction velocity was dependent on the ionic strength of the buffer; decreasing with increasing concentration. The pH optimum was around 7, which is lower than pH-optima described for other kinds of substrates. (32P) phosphorylated fibrinogen was dephosphorylated about 20 times faster than (32P)phosphohistone on a weight basis and the reaction continued linearily with time for the longest time tested (3 hs) even at 37 degrees C. As alkaline phosphatase is present in the blood the possible physiological significance of the dephosphorylation of phosphofibrinogen is discussed.