Alkaline phosphatase was extracted from 5 meningiomas, and several of its biochemical properties were compared with alkaline phosphatase from normal serum a n d extracts of small intestine. T h e meningioma phosphatases behaved in a reasonably homogeneous manner. They were virtually uninhibited by 0.05 M L-phenylalanine a n d were remarkably heat sensitive. One molar urea produced a similar degree of inactivation to that obtained with alkaline phosphatase of normal serum. Electrophoretically the alkaline phosphatase of all meningiomas produced a single band moving a t the same rate as the main band seen in normal serum.
VER THE PAST FEW YEARS THE VARIOUS 0 forms in which alkaline phosphatase isoenzymes can exist in the blood and body tissues have become better understood as the result of differentiation based on electrophoresis on a variety of media, together with heat inactivation,lz urea inhibition,', 2 . 4 and inhibition with L-phenylalanine.5 T h e present investigation was concerned with the characterization of alkaline phosphatase extracted from meningiomas by a modified n-butanol method,lo. 11 and to compare these parameters with 2 known isoenzymes of alkaline phosphatase, i.e., those of small intestine and of normal serum.