Institute of Clinical Pharmacology, Anhui Medical University, The Key Laboratories of Zoonoses and Pathogen Biology, Anhui, Hefei, 230032 Anhui Province, China.
Parasitol Res. 2011 Oct;109(4):1065-74. doi: 10.1007/s00436-011-2347-y. Epub 2011 May 10.
Catecholamines, such as dopamine and noradrenaline, play important roles as neuromuscular transmitters and modulators in all parasitic helminthes, including Schistosoma japonicum. S. japonicum tyrosine hydroxylase (SjTH) was amplified by rapid amplification of cDNA ends polymerase chain reaction that shows strong homology to Schistosoma mansoni tyrosine hydroxylase, the enzyme that catalyzes the first and rate-limiting step in the biosynthesis of catecholamines. The SjTH transcripts encoded the protein of 463 amino acids and a predicted size of 54 kDa. Purified recombinant SjTH as an N-terminal histidine fusion protein expressed in Escherichia coli showed catalytic activity that was confirmed with (3)H tyrosine uptake. The purified enzyme was found to have the same absolute requirement for a tetrahydrobiopterin cofactor and similar sensitivity to be inhibited by high concentration of the substrate, tyrosine, as the mammalian enzyme. Also, purified SjTH showed characteristic inhibition by catecholamine products. The phosphorylated peptide from SjTH could interact with Sj14-3-3 signal protein. This evidence indicates that SjTH encodes a functional tyrosine hydroxylase that has catalytic properties similar to those of the mammalian hosts' enzyme, and its catalytic activity could be regulated by a phosphorylated or dephosphorylated form. This demonstration of SjTH further suggests that the parasites have the enzymatic capacity to synthesize catecholamines endogenously.
儿茶酚胺，如多巴胺和去甲肾上腺素，在包括日本血吸虫在内的所有寄生性蠕虫中作为神经肌肉递质和调节剂发挥着重要作用。日本血吸虫酪氨酸羟化酶（SjTH）通过快速扩增 cDNA 末端聚合酶链反应扩增，与曼氏血吸虫酪氨酸羟化酶具有很强的同源性，后者是儿茶酚胺生物合成中的第一个限速酶。SjTH 转录本编码 463 个氨基酸的蛋白质，预测大小为 54 kDa。从大肠杆菌中表达的 N 端组氨酸融合蛋白纯化的重组 SjTH 表现出催化活性，这通过（3）H 酪氨酸摄取得到证实。纯化的酶对四氢生物蝶呤辅酶具有相同的绝对需求，并且对底物酪氨酸的高浓度抑制的敏感性与哺乳动物酶相似。此外，纯化的 SjTH 表现出特征性的儿茶酚胺产物抑制。SjTH 的磷酸化肽可与 Sj14-3-3 信号蛋白相互作用。这一证据表明 SjTH 编码一种具有与哺乳动物宿主酶相似催化特性的功能性酪氨酸羟化酶，其催化活性可通过磷酸化或去磷酸化形式进行调节。SjTH 的这一证明进一步表明，寄生虫具有内源性合成儿茶酚胺的酶促能力。
