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Cysteamine S-Phosphate Hydrolysis by Pure Human Alkaline Phosphatases and by Sera from Patients with Lymphoproliferative Disorders

Divisions of Medical Laboratory Science and Clinical Pathology, Department of Pathology, University of Alberta, Edmonton, Alberta, Canada

Alkaline phosphatases (EC 3.1.3.1) purified from human placenta, neutrophils, liver, kidney, and small intestinal mucosa showed a range of K_m values for p-nitrophenyl phosphate from 0.017 to 0.038 mM. The K_m values for cysteamine S-phosphate were more variable and ranged from 0.09 to 1.00 mM. The ratios of the rate of hydrolysis of p-nitrophenyl phosphate to the rate of hydrolysis of cysteamine S-phosphate were similar among the multiple forms of human alkaline phosphatase (1.5 to 1.9) with a mean value of 1.7.

The hydrolysis of p-nitrophenyl phosphate and cysteamine S-phosphate was also measured in 36 normal sera, and a mean value of 2.1 ± 0.5 (S.D.) was obtained from the ratios of the rate of hydrolysis of p-nitrophenyl phosphate to that of cysteamine S-phosphate. Forty sera from patients with one of the following lymphoproliferative disorders: lymphoma; myeloma; infectious mononucleosis; Hodgkin's disease; chronic or acute lymphatic leukemia; or Burkitt's lymphoma displayed a mean ratio of 2.0 ± 0.4. The mean ratio for 13 sera from patients with one of the following proliferative disorders, acute myeloid leukemia, lung cancer, or sarcoma, was 2.2 ± 0.3. The sera from nine patients with increased serum alkaline phosphatase levels due to pregnancy or conditions other than proliferative disorders had a mean value of 1.8 ± 0.3 for the ratio of the rate of hydrolysis of p-nitrophenyl phosphate to that of cysteamine S-phosphate. Seventeen aqueous solutions of butanol extracts of either normal granulocytes or lymphocytes had a mean ratio value of 2.0 ± 0.9. Therefore, no evidence was found for a unique alkaline phosphatase which could act as a marker for lymphoproliferative disorders through its inability to hydrolyze cysteamine S-phosphate.

¹ Recipient of a studentship from the Medical Research Council of Canada, and a Research Allowance from the Alberta Heritage Foundation for Medical Research, during the tenure of which part of this work was performed.

² Recipient of a term grant from the Medical Research Council of Canada in partial support of this work.

Received 1/26/82. Accepted 5/28/82.