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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Switching desaturase enzyme specificity by alternate subcellular targeting.
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Switching desaturase enzyme specificity by alternate subcellular targeting.

机译：通过交替的亚细胞靶向切换去饱和酶的特异性。

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The functionality, substrate specificity, and regiospecificity of enzymes typically evolve by the accumulation of mutations in the catalytic portion of the enzyme until new properties arise. However, emerging evidence suggests enzyme functionality can also be influenced by metabolic context. When the plastidial Arabidopsis 16:0Delta7 desaturase FAD5 (ADS3) was retargeted to the cytoplasm, regiospecificity shifted 70-fold, Delta7 to Delta9. Conversely, retargeting of two related cytoplasmic 16:0Delta9 Arabidopsis desaturases (ADS1 and ADS2) to the plastid, shifted regiospecificity approximately 25-fold, Delta9 to Delta7. All three desaturases exhibited Delta9 regiospecificity when expressed in yeast, with desaturated products found predominantly on phosphatidylcholine. Coexpression of each enzyme with cucumber monogalactosyldiacylglycerol (MGDG) synthase in yeast conferred Delta7 desaturation, with 16:1Delta7 accumulating specifically on the plastidial lipid MGDG. Positional analysis is consistent with ADS desaturation of 16:0 on MGDG. The lipid headgroup acts as a molecular switch for desaturase regiospecificity. FAD5 Delta7 regiospecificity is thus attributable to plastidial retargeting of the enzyme by addition of a transit peptide to a cytoplasmic Delta9 desaturase rather than the numerous sequence differences within the catalytic portion of ADS enzymes. The MGDG-dependent desaturase activity enabled plants to synthesize 16:1Delta7 and its abundant metabolite, 16:3Delta(7,10,13). Bioinformatics analysis of the Arabidopsis genome identified 239 protein families that contain members predicted to reside in different subcellular compartments, suggesting alternative targeting is widespread. Alternative targeting of bifunctional or multifunctional enzymes can exploit eukaryotic subcellular organization to create metabolic diversity by permitting isozymes to interact with different substrates and thus create different products in alternate compartments.
机译：酶的功能性，底物特异性和区域特异性通常通过酶催化部分中突变的积累而发展，直到出现新的性质。但是，新出现的证据表明酶的功能也可能受代谢环境的影响。当质体拟南芥16：0Delta7去饱和酶FAD5（ADS3）重新定位到细胞质时，区域特异性转移了70倍，Delta7变为Delta9。相反，将两个相关的胞质16：0Delta9拟南芥去饱和酶（ADS1和ADS2）重新靶向到质体，将区域特异性转移了约25倍，Delta9到Delta7。当在酵母中表达时，所有三种去饱和酶均表现出Delta9区域特异性，去饱和产物主要存在于磷脂酰胆碱上。每种酶与黄瓜单半乳糖基二酰基甘油（MGDG）合酶在酵母中的共表达赋予Delta7去饱和作用，而16：1Delta7专门积聚在质体脂质MGDG上。位置分析与MGDG上的ADS去饱和度为16：0一致。脂质头基充当去饱和酶区域特异性的分子开关。因此，FAD5 Delta7的区域特异性是由于向细胞质Delta9去饱和酶中添加转运肽而不是在ADS酶催化部分内的众多序列差异而导致的酶的质体重新定向。 MGDG依赖的去饱和酶活性使植物能够合成16：1Delta7及其丰富的代谢产物16：3Delta（7,10,13）。对拟南芥基因组的生物信息学分析确定了239个蛋白家族，这些蛋白家族包含预计位于不同亚细胞区室的成员，这表明替代靶向已广泛存在。双功能或多功能酶的替代靶向可以利用真核亚细胞组织，通过允许同工酶与不同的底物相互作用，从而在不同的间隔中产生不同的产物，从而创造代谢多样性。

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