Shioji K, Imai H, Tai J, Ueda I, Tanigawa Y
Biochim Biophys Acta. 1978 Jan 12;522(1):96-103. doi: 10.1016/0005-2744(78)90325-x.
The reversible heat activation and cold inactivation of tyrosine aminotransferase (L-tyrosine:2-oxoglutarate aminotransferase, EC 2.6.1.5) of chick liver were investigated. When the enzyme obtained by gel filtration was preincubated at 37 degrees C for 10 min with 50 micrometer pyridoxal 5'-phosphate (pyridoxal-5'-P), a 7-fold increase in enzyme activity was detected. When the preincubated enzyme was cooled to 0 degrees C, it lost its activity. Furthermore, the dramatic cyclical changes in enzyme activity occurred by sequential heating at 37 degrees C and cooling to 0 degrees C of the enzyme, in the presence of pyridoxal-5'-P, over shorter periods of time without loss of enzyme activity. However, when alpha-ketoglutarate was added to the enzyme during cold exposure, no further decrease in activity was observed. This protective effect was seen at a concentration of 5 muM.
对鸡肝酪氨酸转氨酶（L-酪氨酸：2-氧代戊二酸转氨酶，EC 2.6.1.5）的可逆热激活和冷失活进行了研究。当通过凝胶过滤获得的酶与50微摩尔吡哆醛5'-磷酸（吡哆醛-5'-P）在37℃预孵育10分钟时，检测到酶活性增加了7倍。当将预孵育的酶冷却至0℃时，它失去了活性。此外，在存在吡哆醛-5'-P的情况下，通过在较短时间内将酶依次加热至37℃和冷却至0℃，酶活性发生了显著的周期性变化，且酶活性没有损失。然而，当在冷暴露期间向酶中加入α-酮戊二酸时，未观察到活性进一步降低。在5微摩尔的浓度下可看到这种保护作用。
