Isozymes of alpha-amylase in human urine

Some physicochemical properties of crystalline alpha-amylase [EC 3.2.1.1] isolated from normal human urine were investigated. A crystalline preparation of the enzyme was homogeneous on velocity sedimentation, gel filtration, and sodium dodecyl sulfate disc electrophoresis, and its molecular weight was estimated to be 4.5 X 10-4. However, electrophoretic analyses revealed that the crystalline alpha-amylase consisted of at least five isozymes. The implications of the experimental results are discussed.