Bouvier F, D'harlingue A, Backhaus R A, Kumagai M H, Camara B
Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique and Université Louis Pasteur, Strasbourg, France.
Eur J Biochem. 2000 Nov;267(21):6346-52. doi: 10.1046/j.1432-1327.2000.01722.x.
Neoxanthin, a precursor of the plant hormone abscisic acid, is an allenic xanthophyll recognized as the last product of carotenoid synthesis in green plants. A cDNA for neoxanthin synthase (NSY) was isolated from tomato using a molecular approach based on the mechanistic and structural similarities of NSY to two other closely related carotenogenic enzymes, lycopene cyclase (LCY) and capsanthin-capsorubin synthase (CCS). The identified tomato NSY cDNA (T.NSY) encodes a 56-kDa plastid-targeted protein that when expressed in Escherichia coli, catalyzes the conversion of violaxanthin to neoxanthin. In tobacco leaves that transiently express T.NSY, an increase in neoxanthin content with a concomitant decrease in violaxanthin is observed. NSY is structurally similar to LCY and CCS. However, in Cyanobacteria, the generally accepted progenitor of plastids, both CCS and NSY are absent while LCY is present. LCY catalyzes a simplified version of the reaction catalyzed by NSY and CCS suggesting that these two enzymes were remodeled from LCY during higher plant evolution to create new forms of oxidized carotenoids.
新黄质是植物激素脱落酸的前体，是一种丙二烯叶黄素，被认为是绿色植物中类胡萝卜素合成的最终产物。基于新黄质合酶（NSY）与另外两种密切相关的类胡萝卜素生成酶——番茄红素环化酶（LCY）和辣椒红素 - 辣椒玉红素合酶（CCS）在机制和结构上的相似性，采用分子方法从番茄中分离出了新黄质合酶的cDNA。鉴定出的番茄NSY cDNA（T.NSY）编码一种56 kDa的靶向质体的蛋白质，该蛋白质在大肠杆菌中表达时，催化紫黄质向新黄质的转化。在瞬时表达T.NSY的烟草叶片中，观察到新黄质含量增加，同时紫黄质含量减少。NSY在结构上与LCY和CCS相似。然而，在被普遍认为是质体祖先的蓝细菌中，不存在CCS和NSY，而存在LCY。LCY催化的反应是NSY和CCS催化反应的简化版本，这表明这两种酶是在高等植物进化过程中从LCY改造而来，以产生新形式的氧化类胡萝卜素。
