High‐molecular intestinal alkaline phosphatase by agarose gel electrophoresis

The presence of high‐molecular intestinal ALP (HIALP) overlapping with bone ALP in the α 2 β region has been demonstrated. In this study we evaluated a method of separating HIALP after its conversion into ALP 5 by the action of protease. Serum samples from patients were mixed with protease at a ratio of 5:1 and left at room temperature for more than 30 min. The protease‐treated and nontreated samples were both subjected to agarose gel electrophoresis. Patients who showed a decrease in ALP 3 in the α2β region and an increase in ALP 5 in the β region were regarded as HIALP‐positive. HIALP was observed in 26.7–33.1% of patients with liver diseases, collagen diseases, and diabetes mellitus. Renal disease was ABO blood group‐dependent and showed high positive rates for blood groups B and O. The HIALP‐positive rate was low (7.1–15.5%) in patients with cardiovascular diseases, malignant tumors, and other disorders. ALP 5 was also observed in 98.4% of HIALP‐positive patients with liver diseases. In patients with collagen diseases or diabetes mellitus, the positive rate of ALP 5 was 40.4–66.7%. In conclusion, this method, in which HIALP is converted into ALP 5 by protease pretreatment and is separated from bone ALP, allows HIALP to be identified while other fractions remain unaffected. J. Clin. Lab. Anal. 21:140–146, 2007. © 2007 Wiley‐Liss, Inc.