2.6.1.64 - 639901, 640171, 640172, 640173, 640174, 640175, 640176, 640179, 640181, 640183, 640184 2.6.1.64 native enzyme from rat brain by ultracentrifugation at 220000 x g, followed by ammonium sulfate fractionation, hydropbobic interaction chromatography, anion exchange chromatography, and hydroxyapatite chromatography 759123, 759850