Studies on Two Kinds of Alkaline Phosphatase of Human Placenta

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概要

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• It is evident that no agreement is found in the literature about the nature of alkaline phosphatase. For instance, Binkley, in purifying an alkaline phosphatase from swine kidney, claimed that the enzyme contains no protein, or if any, it is not essential for the activity of the enzyme, whereas Mathies prepared the enzyme containing 12% nitrogen from the same source.<BR>The activity of the enzyme prepared by Mathies was 10,500 units according to the assay of King et al., and that prepared by Binkley was 300,000 Roche units per mg of total nitrogen. According to Schramm and Armbrustar, a factor of about 7 is required to convert King units into Roche units, and thus, the preparation of Mathies would have a specific activity of 10,500×7×1.4 or 102, 800 Roche units, the factor of 1.4 being a coefficient for conversion of the result obtained at 25° into that at 37°.<BR>Ahmed and King isolated an alkaline phosphatase fraction from placenta by the butanol extraction method. They obtained a sample with 1,150 King-Armstrong units/mg N (K-A units/mg N), and further purified it by paper electrophoresis up to 1,750 K-A units/mg N. However, they did not mention the composition of the enzyme. Ghosh and Fishman purified human placental alkaline phosphatase and reported that variant A and crystalline B were obtanined, their molecular weight being 70,000 and 200,000, respectively, and that the activity of the former was 1,71 and the latter 212 units/mg. Harkness reported a crystalline alkaline phosphatase of specific activity of 4,200 units/mg. Since the definition of the specific activity of Ghosh et al. and that of Harkness are different each other, no direct comparison of purity of their preparations are possible.<BR>We purified the enzyme from human placenta under mild condition without using any organic solvents, and obtained two kinds of alkaline phosphatase, A and B. The specific activity of A was 132,000 K-A units/mg N and that B was 38,000 K-A units/mg N. Both A and B samples were glycoprotein. A contains 32% of glucose and 2.8% of sialic acid, and B 1.5% of sialic acid. The optimum tempera-ture, optimum pH and Km were 60°, 10.0 and 3.85×10<SUB>-3</SUB>M in A and 37°, 8.8 and 2×10<SUB>-3</SUB>M in B, respectively. A shows wave shaped change in activity, accompanying change in optical rotatory power during incubation at 37°, and the activity gradually rises as a whole as time passes. On the contrary, the activity of B decreases linearly with time.

• Japan Society of Clinical Chemistryの論文

著者

• 村上 枝彦

  愛知教育大学化学教室

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• Studies on Two Kinds of Alkaline Phosphatase of Human Placenta

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