느타리 버섯의 자실체의 마쇄액을 냉동원십분리하여 세포질, mitochondria 및 핵분획을 각각 분리하여 branched chain amino acid aminotransferase (EC 2.6.1.42)의 분포상태와 몇가지 이화학적 성상을 관찰하여 얻은 결과를 요약하면 다음과 같다. 1. 느타리 버섯의 branched chain amino acid aminotranferase 활성도는 2.79 unit/g으로 흰쥐의 신장의 것과 거의 유사하였다. 2. 느타리 버섯의 branched chain amino acid aminotransferase는 세포질, mitochondria 및 핵의 각 분획에서 발견되었으며 세포질 분획에는 전체 효소 활성도의 약 91.0%, mitochondria에 약 5.0%, 핵 분획에 약 1.8%가 분포되어 있었다. 3. 세포질의 branched chain amino acid aminotransferase를 부분정제하여 DEAE-cellulose column chromatography법으로 그 isozyme의 pattern을 관찰하였던 바 인산염 완충용액 용출액의 농도가 20 mM 및 180 mM에서 Enzyme I 및 Enzyme II가 검출되었을 뿐 Enzyme III은 검출되지 않았다. 4. Enzyme II의 효소활성도는 Enzyme I에 비해 7.0배 정도 높았다. 5. Enzyme I 및 II의 기질(leucine, isoleucine 및 valine)에 대한 효소활성도는 leucine 이 가장 높았다. 6. Enzyme II의 최적 pH는 8.2이고 최적온도는 $35^{circ}C$이며, 열에 대해서는 불안정한 효소이다. 7. Enzyme II의 L-leucine, $alpha$-ketoglutarate 및 pyridoxal phosphate에 대한 Km값은 각각 0.38 mM, 2.86 mM 및 $3.9{ imes}10^{-6};mM$이었다. 8. Gel filtration에 의한 Enzyme II의 분자량은 약 64,000이었다.
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 $35^{circ}C$, respectively: The enzyme was highly unstable above $30^{circ}C$. 7. The Km values for L-Ieucine, $alpha$-ketoglutarate and pyridoxal phosphate of Enzyme II were 0.38 mM, 2.86 mM, and $3.9{ imes}10^{-6};mM$, respectively. 8. The molecular weight of Enzyme II was estimated to be about 64,000 by Sephadex G-200 gel filtration.
