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 10m M Tris‐HCI, pH 7.4. Kinetic measurements have shown that the apparent K m 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 K 1 was determined to be 6.38 × 10 −4 M and the inhibition is uncompetitive. © 1995 John Wiley & Sons, Inc.