TRANSAMINASE OF BRANCHED CHAIN AMINO ACIDS .I. BRANCHED CHAIN AMINO ACIDS-ALPHA-KETOGLUTARATE TRANSAMINASE
TRANSAMINASE OF BRANCHED CHAIN AMINO ACIDS .I. BRANCHED CHAIN AMINO ACIDS-ALPHA-KETOGLUTARATE TRANSAMINASE
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DOI：
10.1093/oxfordjournals.jbchem.a128277
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发表时间：
1966-01-01
影响因子：
2.7
通讯作者：
KOYAMA, E
中科院分区：
文献类型：
--
作者：
ICHIHARA, A;KOYAMA, E
测定了大鼠不同组织中缬氨酸、亮氨酸、异亮氨酸-[α]-酮戊二酸转氨酶活性的分布。结果发现，心脏和肾脏是最活跃的器官的活动，其次是骨骼肌和肝脏显示出非常低的活性。这3种氨基酸中最好的底物是亮氨酸或异亮氨酸，这取决于所用的组织。在所有检查的组织中，缬氨酸是3种中最差的。酶活性的亚细胞分布表明，上清液和线粒体组分都含有活性。对猪心可溶性转氨酶进行了部分纯化，在纯化过程中，3种氨基酸的活性比保持恒定。该酶的最适pH为8.6的3种氨基酸和3种氨基酸，[α] -酮戊二酸和磷酸吡哆醛的同时存在是必不可少的酶活性。该活性被证明是可逆的。热处理使转氨酶失活，3种氨基酸的活性以相同的速率下降。转氨酶的底物特异性主要限于支链氨基酸，但正缬氨酸和正亮氨酸表现出较小的活动。其他检查的氨基酸均无活性。缬氨酸，亮氨酸和异亮氨酸被证明是竞争型底物，它是从这些研究结果得出的结论是，转氨酶研究是特定的支链氨基酸和3种氨基酸的转氨酶由相同的酶。
The distribution of valine, leucine, isoleucine-[alpha]-ketoglutarate transaminase activity was determined in various tissues of rats. It was found that heart and kidney were the most active organs for the activity, followed by skeletal muscle and that liver showed very low activity. The best substrate among these 3 amino acids was either leucine or isoleucine depending upon the tissue used. Valine was the poorest of the 3 in all tissues examined. The sub-cellular distribution of enzyme activity in rat heart showed that both the supernatant and mitochondrial fractions contained activity. The partial purification of soluble transaminase from hog heart was carried out and during the purification procedures the activity ratios for the 3 amino acids remained constant. The enzyme had an optimal pH at 8.6 for the 3 amino acids and the simultaneous presence of 1 of the 3 amino acids, [alpha] -ketoglutarate and pyridoxal phosphate was essential for the enzyme activity. The activity was shown to be reversible. The transaminase was inactivated by heat treatment and the activity for the 3 amino acids decreased at the same rate. The substrate specificity for the transaminase was chiefly limited to branched chain amino acids, but norvaline and norleucine showed lesser activities. Other amino acids examined were all inactive. Valine, leucine and isoleucine were shown to be competitive type substrates and it was concluded from these findings that the transaminase studied was specific for branched chain amino acids and the 3 amino acids were transaminated by the same enzyme.