Ben Jin, Lim Tit Meng, Phang Violet P E, Chan Woon-Khiong
Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Republic of Singapore.
Mar Biotechnol (NY). 2003 Nov-Dec;5(6):568-78. doi: 10.1007/s10126-002-0121-y. Epub 2003 Aug 21.
Guppy is a popular ornamental fish owing to its diverse body and fin coloration. More than 40 established color varieties have been selectively bred. The complementary DNAs for 2 enzymes that are involved in the de novo synthesis of pteridines and purines, which are important for the production of color pigments, were cloned from the caudal fin. Two cDNA isoforms for 6-pyruvoyl tetrahydropterin synthase (PTPS), with an open reading frame of 130 and 147 amino acids, respectively, were cloned from the Red Tail variety. The deduced amino acid sequence of the longer isoform shows an overall identity of about 65% to the mammalian PTPS sequences. The cDNA for xanthine dehydrogenase (XDH) was cloned from the Yellow Tail variety, and consists of an open reading frame of 1331 amino acids. Although it shows a higher overall identity to bovine aldehyde oxidase (AO; 54%) than to chicken XDH (51%), it has a NAD-binding domain that is specific to XDHs. Northern blot analysis indicated that both PTPS and XDH messenger RNAs were highly expressed in the liver, but absent in the muscle. In the caudal fins, guppy varieties with a higher proportion of xanthophores and erythrophores showed higher expression of PTPS, while XDH mRNA levels were too low to indicate obvious differential expression among the color guppy varieties. The results implied that high expression of PTPS is correlated with the biosynthesis of pteridines in the erythrophores and xanthophores, while the association between the putative guppy XDH with specific chromatophores is less clear.
孔雀鱼因其多样的体色和鳍色而成为一种受欢迎的观赏鱼。人们已经选择性培育出了40多个已确立的颜色品种。从尾鳍中克隆出了参与蝶啶和嘌呤从头合成的2种酶的互补DNA，蝶啶和嘌呤对色素的产生很重要。从红尾品种中克隆出了6-丙酮酸四氢蝶呤合酶（PTPS）的两种cDNA异构体，其开放阅读框分别为130和147个氨基酸。较长异构体的推导氨基酸序列与哺乳动物PTPS序列的总体一致性约为65%。从黄尾品种中克隆出了黄嘌呤脱氢酶（XDH）的cDNA，其由1331个氨基酸的开放阅读框组成。尽管它与牛醛氧化酶（AO；54%）的总体一致性高于与鸡XDH（51%）的一致性，但它具有XDH特有的NAD结合结构域。Northern印迹分析表明，PTPS和XDH信使RNA在肝脏中高度表达，但在肌肉中不存在。在尾鳍中，黄色素细胞和红色素细胞比例较高的孔雀鱼品种显示出PTPS的较高表达，而XDH mRNA水平过低，无法显示出在不同颜色孔雀鱼品种之间有明显的差异表达。结果表明，PTPS的高表达与红色素细胞和黄色素细胞中蝶啶的生物合成相关，而推测的孔雀鱼XDH与特定色素细胞之间的关联尚不清楚。
