Large scale purification of myo‐inositol monophosphate phosphatase from porcine brains

myo‐Inositol monophosphate phosphatase (IMPase) has been purified 888‐fold to apparent homogeneity from procine brains. The purification procedure involves: homogenization, ammonium sulfate fractionation, and a number of ion‐exchange and gel‐filtration chromatography steps. The purified enzyme exhibited a final specific activity of 932 nmol · min−1 · mg−1. The molecular mass of the enzyme was estimated to be 29kDa by SDS poly‐acrylamide gel electrophoresis and 58 ± 5 kDa by HPLC gel filtration in 10mM Tris‐HCI, pH 7.4. Kinetic measurements have shown that the apparent Km value of the phosphatase for the utilization of inositol‐1‐phosphate and β‐glycerol phosphate are 3.20 × 10−4 and 8 × 10−3 M, respectively. Similar to the same enzyme isolated from bovine brains, the porcine brain enzyme has been shown to be inhibited by lithium. The K1 was determined to be 6.38 × 10−4 M and the inhibition is uncompetitive.