色氨酸羟化酶2(TPH2)催化L-色氨酸羟化为L-5-羟色氨酸(5-HTP),哺乳动物大脑中5-HT合成的第一步和关键步骤。降低酶活性的人Tph2基因中的突变增加了精神病理学的风险。药物伴侣是可以特异性结合突变蛋白分子的小分子,将受干扰的3D结构恢复到原始状态,并增加其稳定性和功能活性。(R)-2-氨基-6-(1R,2S)-1,2-二羟丙基)-5,6,7,8-四氢蝶呤-4(3H)-酮(BH4)通过增加突变酪氨酸羟化酶和苯丙氨酸羟化酶分子的体外热稳定性来表达,这些分子在结构和特性上与TPH2相似。小鼠TPH2分子中的P447R取代导致其脑中酶活性降低2倍。我们研究了这种突变对TPH2热稳定性的影响,以及BH4及其8种结构类似物增加来自BALB/C小鼠中脑提取物的突变体TPH2的热稳定性的能力。通过在升高的温度下加热2分钟期间酶活性的降低来研究温度稳定性,并通过T50值进行评估,T50值是酶活性降低一半的温度。对于突变体TPH2,与野生型酶相比,T50值降低。BH4及其最接近的结构类似物,6-甲基-5,6,7,8-四氢蝶呤,增加了T50值,即,表现出伴侣活动。其他接近BH4类似物,6,7-二甲基-5,6,7,8-四氢蝶呤和叶酸,没有效果。可以认为BH4可以有效治疗由Tph2基因突变引起的精神障碍。
The enzyme tryptophan hydroxylase 2 (TPH2) catalyzes the hydroxylation of L-tryptophan to L-5-hydroxytryptophan (5-HTP), the first and the key step in 5-HT synthesis in the mammalian brain. Mutations in the human Tph2 gene reducing enzyme activity increase the risk of psychopathology. Pharmacological chaperones are small molecules that can specifically bind to mutant protein molecules, restore their disturbed 3D structure to the native state, and increase their stability and functional activity. The chaperone activity of (R)-2-amino-6-(1R,2S)-1,2-dihydroxypropyl)-5,6,7,8-tetrahydropterin-4(3H)-one (BH4) is expressed by increasing the in vitro thermal stability of mutant tyrosine hydroxylase and phenylalanine hydroxylase molecules which are similar to TPH2 in their structure and characteristics. The P447R substitution in the mouse TPH2 molecule results in a 2-fold decrease in enzyme activity in their brains. We studied the effect of this mutation on the TPH2 thermal stability, as well as on the ability of BH4 and its 8 structural analogues to increase the thermal stability of the mutant TPH2 from midbrain extracts of BALB/C mice. Temperature stability was studied by the decrease in enzyme activity during its heating for 2 min at increasing temperatures and was evaluated by the T50 value that is the temperature at which the enzyme activity decreased by half. For the mutant TPH2, the T50 value was decreased compared to the wild type enzyme. BH4 and its closest structural analogue, 6-methyl-5,6,7,8-tetrahydropterin, increased the T50 value, i.e., exhibited chaperone activity. Other close BH4 analogs, 6,7-dimethyl-5,6,7,8-tetrahydropterin and folic acid, were not effective. It can be assumed that BH4 can be effective in the treatment of mental disorders caused by mutations in the Tph2 gene.