Chen Ping, Wang Jiying, Li Haiyin, Li Yan, Chen Peng, Li Tian, Chen Xi, Xiao Junjie, Zhang Liang
College of Biotechnology, Southwest University, Chongqing 400716, China.
College of Biotechnology, Southwest University, Chongqing 400716, China.
Gene. 2015 Aug 10;567(2):138-45. doi: 10.1016/j.gene.2015.03.043. Epub 2015 May 7.
In insects, pigment patterns are formed by melanin, ommochromes, and pteridines. Here, the effects of pteridine synthesis on melanin formation were studied using 4th instar larvae of a wild-type silkworm strain, dazao (Bombyx mori), with normal color and markings. Results from injected larvae and in vitro integument culture indicated that decreased activity of guanosine triphosphate cyclohydrolase I (GTP-CH I, a rate-limiting enzyme for pteridine synthesis), lowers BH4 (6R-l-erythro-5,6,7,8-tetrahydrobiopterin, a production correlated with GTP-CH I activity) levels and eliminates markings and coloration. The conversion of phenylalanine and tyrosine to melanin was prevented when GTP-CH I was inhibited. When BH4 was added, phenylalanine was converted to tyrosine, and the tyrosine concentration increased. Tyrosine was then converted to melanin to create normal markings and coloration. Decreasing GTP-CH I activity did not affect L-DOPA (3,4-l-dihydroxyphenylalanine). GTP-CH I affected melanin synthesis by generating the BH4 used in two key reaction steps: (1) conversion of phenylalanine to tyrosine by PAH (phenylalanine hydroxylase) and (2) conversion of tyrosine to L-DOPA by TH (tyrosine hydroxylase). Expression profiles of BmGTPCH Ia, BmGTPCH Ib, BmTH, and BmPAH in the integument were consistent with the current findings.
在昆虫中，色素模式由黑色素、眼色素和蝶啶形成。在此，我们使用具有正常颜色和斑纹的野生型家蚕品系大造（Bombyx mori）的四龄幼虫，研究了蝶啶合成对黑色素形成的影响。注射幼虫和体外体壁培养的结果表明，鸟苷三磷酸环化水解酶I（GTP-CH I，蝶啶合成的限速酶）活性降低，会降低BH4（6R-l-赤藓糖-5,6,7,8-四氢生物蝶呤，一种与GTP-CH I活性相关的产物）水平，并消除斑纹和色素沉着。当GTP-CH I受到抑制时，苯丙氨酸和酪氨酸向黑色素的转化被阻止。添加BH4后，苯丙氨酸转化为酪氨酸，酪氨酸浓度增加。然后酪氨酸转化为黑色素，形成正常的斑纹和色素沉着。降低GTP-CH I活性并不影响L-DOPA（3,4-l-二羟基苯丙氨酸）。GTP-CH I通过生成两个关键反应步骤中使用的BH4来影响黑色素合成：（1）苯丙氨酸羟化酶（PAH）将苯丙氨酸转化为酪氨酸，以及（2）酪氨酸羟化酶（TH）将酪氨酸转化为L-DOPA。体壁中BmGTPCH Ia、BmGTPCH Ib、BmTH和BmPAH的表达谱与当前研究结果一致。
