Catalytic activities and chloroplast import of carotenogenic enzymes from citrus
Catalytic activities and chloroplast import of carotenogenic enzymes from citrus
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DOI：
10.1111/j.1399-3054.2006.00690.x
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发表时间：
2006-08-01
影响因子：
6.4
通讯作者：
Ikoma, Yoshinori
中科院分区：
文献类型：
--
作者：
Inoue, Kentaro;Furbee, Kendra J.;Ikoma, Yoshinori
柑橘类水果富含类胡萝卜素。类胡萝卜素生物合成酶的cDNA已经从它们的外果皮和汁囊中鉴定出来，并被几个研究小组用于研究果实发育过程中类胡萝卜素基因的表达模式。然而，大多数基因产物的功能尚未得到证实。本论文研究了脐橙橙子（Citrus sinensis Osbeck）中的两种胡萝卜素生成酶八氢番茄红素脱氢酶（CitPds）和番茄红素-β-环化酶（CitLcyb）以及温州蜜柑（Citrus unshiu Marcow）中的一种酶番茄红素-F-环化酶（CitLcye）的催化活性。我们还进行了体外输入测定的三种蛋白质沿着与其他两个从脐橙橙子，八氢番茄红素合成酶（CitPsy）和类胡萝卜素β-环羟化酶（CitChyb），使用分离的叶绿体，并确认其质体定位和运输肽的存在下，进口时被切割。此外，我们还研究了它们的亚细胞器定位。发现CitPsy与膜外周相关，而CitPds主要在可溶性级分中回收。相比之下，CitLcyb和CitLcye的目标都是可溶性和膜室，虽然后者表现出更强的协会比前者的膜。最后，CitChyb专门插入叶绿体内膜。这些数据有助于我们更好地了解类胡萝卜素生物合成的机制。
Citrus fruits are a rich source of carotenoids. cDNAs for carotenoid biosynthetic enzymes have been identified from their flavedos and juice sacs, and were used to examine expression patterns of carotenogenic genes during fruit development by several groups. However, functions of most of the gene products have not been verified yet. in this report, we examined catalytic activities of two carotenogenic enzymes from navel orange (Citrus sinensis Osbeck), phytoene desaturase (CitPds) and lycopene-beta-cyclase (CitLcyb), and one enzyme from Satsuma mandarin (Citrus unshiu Marcow), lycopene-F-cyclase (CitLcye). We also conducted in vitro import assay of the three proteins along with two other carotenogenic enzyme from navel orange, phytoene synthase (CitPsy) and carotenoid beta-ring hydroxylase (CitChyb), using isolated chloroplasts, and confirmed their plastid localization and the presence of transit peptides that were cleaved upon import. Furthermore, we examined their suborganellar localization. CitPsy was found to be peripherally associated with the membrane, while CitPds was mainly recovered in the soluble fraction. By contrast, CitLcyb and CitLcye were targeted both to the soluble and to the membrane compartments, although the latter showed a stronger association to the membrane than the former. Finally, CitChyb was exclusively inserted into the chloroplast internal membranes. These data should help us better understand the mechanism of carotenoid biosynthesis.