Ohisalo J J, Pispa J P
Biochim Biophys Acta. 1975 Jul 27;397(1):94-100. doi: 10.1016/0005-2744(75)90182-5.
The regulation of hepatic tyrosine aminotransferase (L-tyrosine:2-oxoglutarate aminotransferase, EC 2.6.1.5) in the rat has been extensively studied but little is known about the enzyme from other sources. We have studied the regulation of this enzyme in the frog Rana temporaria and in this paper we report that: 1. Cortisone acetate, adrenocorticotropic hormone and alpha-methyl-p-tyrosine, an agent known to induce hepatic tyrosine aminotransferase in the rat via activation of the pituitary-adrenal axis, have no effect on the activity of the enzyme in the frog. 2. Dibutyryl-3',5'-cyclic AMP induces the enzyme to about 2-fold. 3. Injection of tyrosine methyl ester and a protein-rich diet result in an increase in the enzyme activity. This increase is of the same order of magnitude as that caused by dibutyryl cyclic AMP. 4. Glucose significantly reduces tyrosine aminotransferase activity in frog liver. These results suggest that cyclic AMP induces the enzyme via a mechanism independent of glucocorticoids. The frog offers a model for studies on the regulation of hepatic tyrosine aminotransferase in vivo without interference from secondary effects mediated by the adrenals.
大鼠肝脏中酪氨酸转氨酶（L-酪氨酸：2-氧代戊二酸转氨酶，EC 2.6.1.5）的调节已得到广泛研究，但对于来自其他来源的该酶却知之甚少。我们研究了这种酶在青蛙（林蛙）中的调节情况，并且在本文中报告如下：1. 醋酸可的松、促肾上腺皮质激素以及α-甲基-p-酪氨酸（一种已知通过激活垂体-肾上腺轴诱导大鼠肝脏酪氨酸转氨酶的物质）对青蛙体内该酶的活性没有影响。2. 二丁酰-3',5'-环磷酸腺苷可使该酶的活性诱导至约2倍。3. 注射酪氨酸甲酯和富含蛋白质的饮食会导致该酶活性增加。这种增加与二丁酰环磷酸腺苷所引起的增加幅度相当。4. 葡萄糖可显著降低青蛙肝脏中酪氨酸转氨酶的活性。这些结果表明，环磷酸腺苷通过一种独立于糖皮质激素的机制诱导该酶。青蛙为体内研究肝脏酪氨酸转氨酶的调节提供了一个模型，不受肾上腺介导的次级效应的干扰。
