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KMID : 0360419840200010067
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Korean Journal of Pharmacology
1984 Volume.20 No. 1 p.67 ~ p.74
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Studies on the Alkaline Phosphatase Isoenzymes in Rat Serum and Organs
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Kim Won-Joon
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Abstract
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Alkaline phosphatase is a glycoprotein, and is widely distributed in intestinal mucosa, liver, kidney, pancreas, lung, placenta, bone and blood.
Fishman and his coworker(1968) characterized alkaline phosphatase from intestine and placenta using neuramidase and determined different optimum pH, Km values, showing the possibilities to identify tissue source of serum alkaline phosphatase.
Furthermore, alkaline phosphatases from different sources have different antigenic proper-ties.
The separation of alkaline phosphatase isoenzymes by electrophoresis on starch gel, agar gel, and cellulose acetate has been only partially successful. For example, the isoenzymes obtained from bone and liver diseases have migrated at nearly identical distances on these separation media.
By polyacrylamide gel electrophoresis, however, human serum alkaline phosphatases were found to have four distinct isoenzymes.
The activity of serum alkaline phosphatase was increased in bone diseases associated with increased osteoblastic activity and in certain disorders of liver and biliary tract. This result from the release of tissue-specific alkaline phosphatase. In addition to this, a wide variety of tumor has been shown to secrete alkaline phosphatase into the blood.
Isoenzymes of alkaline phosphatase from different tissues of rat were purified and their isoelectric points were determined. Isoelectric points of these purified iscenzymes from liver,. intestine, pancreas and bone were compared with those of serum.
1) Extracts obtained from homogenized tissues were centrifuged at 65, 000 x g and filtered through an Ultrogel AcA 34 column. Among the 3 major peaks obtained by gel filtration, second peak fractions were further separated by isoelectric focusing. Isoenzymes of alkaline phosphatase were localized only in the second peak.
2) Isoenzymes of alkaline phosphatase were distinguishable even with pH 3.5-10 ampholytes. However, when pH 3-r6 ampholytes were used, isoenzymes were clearly separated.
3) In the serum, there were 4 isoenzymes of alkaline phosphatase. In the intestinal extracts,. 5 isoenzymes of alkaline phosphatase. Where the isoelectric points of these isoenzymes were compared, only the hand with 5.04 pI was the same between serum and intestine.
4) Alkaline phosphatase isoenzymes from liver, pancreas, and bone were separated into two bands.
These results indicate that some of the isoenzymes of alkaline phosphatase found in serum originate from intestine.
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