Isolation and characterization of phosphatases from vascular smooth muscle

Actomyosin preparations of the carotid arteries of cattle contain a soluble phosphatase activity, which can be removed from the contractile proteins by repeated washings. This enzyme activity is lowered by high ionic strength, potassium fluoride, zinc acetate, ammonium molybdate, and vanadate. Magnesium ions enhance the enzyme activity. The phosphatase activity shows a maximum between pH 5.5 and 6.0 and a plateau of pH 7-9. By means of gel filtration on Sepharose 6B the phosphate activity is separated into three peaks, which are characterized with respect to their inhibition by potassium fluoride, ammonium molybate, and vanadate and their dependence on pH.