Oravec M
J Biol Chem. 1975 Jul 10;250(13):5049-52.
DL-alpha-Methyltryptophan (alphaMeTrp), a synthetic analogue of tryptophan, has been found to be a potent inducer of hepatic tyrosine aminotransferase activity in the adrenalectomized rat. alphaMeTrp is inactive in vitro. Unlike the action of other known inducers (tryptophan, hydrocortisone, adenosine cyclic 3:5-monophosphate, and glucagon), maximal stimulation of enzyme activity occurs only 16 to 30 hours after alphaMeTrp administration and the activity is still elevated at 96 hours. Only the L isomer of alphaMeTrp is active, and addition of a hydroxyl group to position 5 of the indole ring renders an inactive compound. The induction can be prevented by actinomycin D or cycloheximide but not galactosamine. Administration of alphaMeTrp together with hydrocortisone produced an additive stimulation of enzyme activity. alphaMeTrp given along with glucagon or adenosine cyclic 3:5-monophosphate caused a further but not additive increase in enzyme activity. Tryptophan given along with alphaMeTrp promoted no extra stimulation whatsoever. These data indicate that alphaMeTrp and tryptophan may act via a common pathway which in part requires RNA synthesis. Other enzymes, namely alanine and aspartate aminotransferase, ornithine aminotransferase, ornithine carbamoyltransferase, serine dehydratase, and histidine ammonialyase, were not affected by treatment of rats with alphaMeTrp.
DL-α-甲基色氨酸（αMeTrp）是色氨酸的一种合成类似物，已发现它是去肾上腺大鼠肝酪氨酸转氨酶活性的强效诱导剂。αMeTrp在体外无活性。与其他已知诱导剂（色氨酸、氢化可的松、环磷腺苷和胰高血糖素）的作用不同，αMeTrp给药后仅16至30小时酶活性出现最大刺激，且在96小时时活性仍升高。只有αMeTrp的L异构体有活性，并且在吲哚环的5位添加一个羟基会产生一种无活性的化合物。放线菌素D或环己酰亚胺可阻止这种诱导，但半乳糖胺不能。αMeTrp与氢化可的松一起给药会产生酶活性的相加刺激。αMeTrp与胰高血糖素或环磷腺苷一起给药会使酶活性进一步增加，但不是相加增加。αMeTrp与色氨酸一起给药不会产生额外刺激。这些数据表明，αMeTrp和色氨酸可能通过一条部分需要RNA合成的共同途径起作用。其他酶，即丙氨酸转氨酶、天冬氨酸转氨酶、鸟氨酸转氨酶、鸟氨酸氨甲酰转移酶、丝氨酸脱水酶和组氨酸解氨酶，不受用αMeTrp处理大鼠的影响。
