Identification and characterization of a mammalian enzyme catalyzing the asymmetric oxidative cleavage of provitamin A
Identification and characterization of a mammalian enzyme catalyzing the asymmetric oxidative cleavage of provitamin A
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DOI：
10.1074/jbc.m011510200
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发表时间：
2001-04-27
影响因子：
4.8
通讯作者：
von Lintig, J
中科院分区：
文献类型：
--
作者：
Kiefer, C;Hessel, S;von Lintig, J
在脊椎动物中，在维生素A及其衍生物的生物合成中，β-胡萝卜素的对称和不对称裂解一直存在争议。最近，我已经从果蝇中鉴定出一个编码后生动物β，β-胡萝卜素-15，15‘-双加氧酶的基因，这种酶催化维生素A生物合成的关键步骤，对称地裂解β-胡萝卜素得到两个分子的视网膜，相应基因的突变被认为会导致盲目的，维生素A缺乏的表型，最近在脊椎动物中也发现了这种酶的同源基因，并进行了分子特征分析。在这里，我们报告了从小鼠中鉴定出编码第二种类型的胡萝卜素双加氧酶的cDNAs，该cDNA专一催化β-胡萝卜素在9‘，10’-双键上的不对称氧化裂解，并导致β-apo-10‘-胡萝卜素和β-紫罗兰酮的形成，例如，玫瑰中的一种被称为花香的物质。除了β-胡萝卜素，番茄红素也被酶氧化分解。推导出的氨基酸序列与β，β-胡萝卜素-15，15‘双加氧酶有显著的同源性，并且这两种酶都有几个保守的基序，为了确定它在不同脊椎动物中的存在，我们尝试并成功地从人和斑马鱼中克隆了编码这种新型胡萝卜素双加氧酶的cDNA作为网，关于它们可能的作用，这种酶形成的脱胡萝卜素可能是维甲酸生物合成的前体或发挥未知的生理作用。因此，与果蝇相反，在脊椎动物中，胡萝卜素的对称和不对称裂解途径都存在，这揭示了胡萝卜素代谢的更复杂。
In vertebrates, symmetric versus asymmetric cleavage of beta -carotene in the biosynthesis of vitamin A and its derivatives has been controversially discussed. Recently me have been able to identify a cDNA encoding a metazoan beta,beta -carotene-15,15'-dioxygenase from the fruit fly Drosophila melanogaster, This enzyme catalyzes the key step in vitamin A biosynthesis, symmetrically cleaving beta -carotene to give two molecules of retinal, Mutations in the corresponding gene are known to lead to a blind, vitamin A-deficient phenotype, Orthologs of this enzyme have very recently been found also in vertebrates and molecularly characterized. Here we report the identification of a cDNA from mouse encoding a second type of carotene dioxygenase catalyzing exclusively the asymmetric oxidative cleavage of beta -carotene at the 9',10' double bond of beta -carotene and resulting in the formation of beta -apo-10'-carotenal and beta -ionone, a substance known as a floral scent from roses, for example. Besides beta -carotene, lycopene is also oxidatively cleaved by the enzyme. The deduced amino acid sequence shares significant sequence identity with the beta,beta -carotene-15,15' dioxygenases, and the two enzyme types have several conserved motifs, To establish its occurrence in different vertebrates, we then attempted and succeeded in cloning cDNAs encoding this new type of carotene dioxygenase from human and zebrafish as web, As regards their possible role, the apocarotenals formed by this enzyme may be the precursors for the biosynthesis of retinoic acid or exert unknown physiological effects. Thus, in contrast to Drosophila, in vertebrates both symmetric and asymmetric cleavage pathways exist for carotenes, revealing a greater complexity of carotene metabolism.