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KMID : 0377519840090020167
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Chung-Ang Journal of Medicine
1984 Volume.9 No. 2 p.167 ~ p.176
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Studies on the Branched Chain Amino Acid Aminotransferase from AH-66 Hepatoma Ascites Cells
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Joh Chang-Muk
Lee Hi-Sung
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Abstract
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The activity and isozyme patterns of branched chain amino acid aminotransferase (EC 2.6.1.6) in AH-66 hepatoma ascites cells which were harvested at 7 days after transplantation have been studied. Isozyme patterns of this enzyme were examined using DEAE-cellulose column chromatography. The results obtained were as follows: 1. In the AH-66 hepatoma ascites cells, the transaminase activities for branched chain amino acids were relatively high than those in rat tissues. 2. The distribution of branched chain amino acid aminotransferase in the subcellular organelles showed that 53% of the activity was in cytosolic fraction, 32% in mitochondrial fraction and 16% in nucleic fraction. 3. Isoleucine was the best substrate among the three branched chain amino acids for the enzyme. 4. Cytosolic fraction of AH-66 hepatoma ascites cells contained isozyme Ⅰ, but not isozyme Ⅱ and Ⅲ, of branched chain amino acid aminotransferase. Isozyme Ⅰ was eluted by 20mM phosphate buffer from DEAE-cellulose column and catalyzed the transamination of all three branched chain amino acids. 5. The optimal temperature for the activity of the isozyme Ⅰ was about 45℃ and the optimal pH was 8.0. 6. The Km values of isozyme Ⅰ for leucine, isoleucine and valine were 1.56, 1.09 and 1.49mM, respectively. 7. The Km values of isozyme Ⅰ for a-ketoglutarate and pyridoxal phosphate were 0.32 and 0.012mM, respectively.
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