Human kidney and urinary alkaline phosphatases.

1. Four fractions of kidney alkaline phosphatase were prepared by chromatography on DEAE-Sephadex. An investigation of their properties suggests that the fractions represent modifications of a single kidney enzyme. 2. Urinary alkaline phosphatase resembles kidney enzyme in most of its properties, but differs in K(m) and in the degree by which it is activated by Mg(2+) ions. 3. Estimates of the molecular weights of kidney and urinary alkaline phosphatase gave values of 150000-170000 for kidney phosphatase and 75000 for the urinary enzyme. 4. It is suggested that urinary alkaline phosphatase is a sub-unit of kidney phosphatase, but it has not been possible to simulate the formation of urinary enzyme by treating kidney enzyme with urea or H(+) ions.