Properties of alkaline-phosphatase fractions in extracts of human small intestine

1. The chromatographic and electrophoretic heterogeneity of human-intestinal alkaline-phosphatase activity is described. 2. The phosphatase activity has been divided into two main components, of which certain properties have been compared. The components resemble each other in their Michaelis constants for the hydrolysis of phenyl phosphate and in their behaviour towards certain inhibitors, but differ in their stability to heat. 3. The addition of Mg²⁺ or Ca²⁺ ions to the electrophoresis buffers sharpens the electrophoretic zones. 4. The results presented do not support the existence of more than one alkaline phosphatase in small intestine.