Copper-resistant serum acid phosphatase. I. Method and values in health and disease.

Human serum contains a mixture of phosphomonoesterases derived from several types of cells with optimum activity at pH 5.0. Clinical assay methods in current use have been developed pri marii}7 to measure acid phosphatases of prostatic origin in metastatic prostatic cancer (10, 11, 15, 30, 34), although increased serum acid phosphatase activity has been noted in patients with neo plasms disseminating from other organs. The availability of a simple and fairly accurate assay procedure for acid phosphatase activity in serum contributed materially to the discovery of antiandrogen therapy for advanced prostatic car cinoma by Dr. C. B. Huggins (13), and there is a serious need at present for other types of serum enzyme assays which provide an objective indica tion of the response of malignant tumors to various types of therapy. The use of tartrate ion for more accurate estimation of prostatic phosphatase (1, 9) and the investigation of serum lactic dehydrogenase (12), serum phosphohexose isomerase (7), and aldolase (2) represent some of the newer con tributions in the field of serum enzyme studies in cancer. These studies may also shed light upon the biochemical alterations accompanying neoplasia. Abul-Fadl and King have investigated numer ous possible inhibitors for the differentiation of various types of serum acid phosphatases and showed that 0.2 mM copper ion quantitatively in hibited enzyme diffusing from erythrocytes (1). Variable amounts of erythrocyte phosphatase ac tivity were noted as an uncontrolled variable in