High-molecular intestinal alkaline phosphatase by agarose gel electrophoresis

The presence of high‐molecular intestinal ALP (HIALP) overlapping with bone ALP in the α2β region has been demonstrated. In this study we evaluated a method of separating HIALP after its conversion into ALP5 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 ALP3 in the α2β region and an increase in ALP5 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. ALP5 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 ALP5 was 40.4–66.7%. In conclusion, this method, in which HIALP is converted into ALP5 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.