느타리버섯의 Branched Chain Amino Acid Aminotransferase 에 관한 연구 = Studies on the Branched Chain Amino Acid Aminotransferase from Oyster Mushroom ( Pleurotus sajor - caju ( Fr . ) Sing )

다국어 초록 (Multilingual Abstract)

Distribution and some properties of branched chain amino acid aminotransferase (EC 2. 6.1. 42) in oyster mushroom have been studied. Oyster mushroom was fractionated into nucleic, mitochondrial and cytosolic fractions by differential centrifugation. Isozyme pattern of this enzyme was also examined by DEAE-cellulose column chromatography. The results obtained are summarized as follows; 1. Total activity of branched chain amino acid aminotransferase in homogenate was 2.79 unit per fresh weight gram. 2. The enzyme was found to be localized in the cytosolic, mitochondrial and nucleic fraction. About 91.0% of the total activity was found in the cytosolic fraction, 5.0% in the mitochondrial fraction and 1.8% in the nucleic fraction. 3. Cytosolic fraction of oyster mushroom was proven to contain Enzyme I and II, but not Enzyme III of branched chain amino acid aminotransferase. Enzyme I was eluted by 20 mM phosphate buffer from DEAE-cellulose column and catalyzed the transamination of the two branched chain amino acids (L-leucine and L-isoleucine). Enzyme II was eluted by 180 mM phosphate buffer and was specific for L-leucine. 4. It was found that the activity of Enzyme II was higher than Enzyme I when L-leucine was used as a substrate. 5. Enzyme II was purified about 54-folds after chromatography on DEAE-cellulose. 6. Optimum pH and temperature from the activity of the Enzyme II were about pH 8.2 and 35℃, respectively: The enzyme was highly unstable above 30℃. 7. The Km values for L-leucine, a-ketoglutarate and pyridoxal phosphate of Enzyme II were 0. 38 mM, 2. 86 mM, and 3. 9 x 10-6 mM, respectively. 8. The molecular weight of Enzyme II was estimated to be about 64,000 by Sephadex G-200 gel filtration.