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KMID : 0376219800170020519
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Chonnam Medical Journal
1980 Volume.17 No. 2 p.519 ~ p.529
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P1OSPHOPROTEIN-PHOSPHATASE ACTIVITY OF HUMAN PLACENTAL ALKALINE PHOSPHATASE
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李民化/Lee, Min-wha
安鳳煥/李起榮/曺仲東/Ahn, Bong-whan/Lee, Kee-young/Cho, Joong-dong
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Abstract
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A purified preparation of human placental alkaline phosphatase has been shown to dephosphorylate casein at physiological pH. It was demonstrated that the casein phosphatase activity was co-purified with the alkaline phosphatase throughout the purification procedures, indicating that the activity of alkaline-phosphatase on casein and on p-nitrophenyl phosphate was apparently due to the same enzyme. These two activities, however, exhibited distinct pH-activity profile, metal ion specificity, response-to inhibitors, and thermostability: case in phosphatase activity was maximal around pH 7.5 to pH 8.5, inhibited by MgC12, and insensitive to the inhibition-by L-phenylalanine and L-tryptophan, whereas p-nitrophenyl phosphatase activity was maximal at pH 10, activated by MgC12, and inhibited by L-phenylalanine and L-tryptophan. Furthermore, the casein phosphatase activity was more heat-stable, and more markedly inhibited by AMP or ATP than p-nitrophenyl phosphatase activity.
The close association of casein phosphatase activity with placental alkaline phosphatase suggests that it may play a role in the regulation of protein phosphorylation-dephosphorylation reaction in vivo.
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