近日，三位美国科学家开展的"酿酒酵母代谢通路整合于线粒体提高支链醇产量"取得阶段性进展，其研究论文Compartmentalization of metabolic pathways in yeast mitochondria improves the production of branched-chain alcohols，近日在Nature Biotechnology杂志发表。
异丁醇在工业上有广泛的应用，因为其热值高、性能好、使用便捷等优势而成为生物能源领域的热点。如何进一步通过技术手段进一步提高产量成为了摆在科学家面前的难题。
研究人员通过将酵母中异丁醇的代谢通路全部整合于线粒体内并进行过表达，在线粒体内即可产生异丁醇而不需要代谢通路的中间代谢物α-KIV跨膜进入细胞质继续进行反应。通过多种发酵实验证明将异丁醇代谢过程中的5个酶过表达，并把其中的2种酶KDC和ADH酶靶向到线粒体中能够明显提高异丁醇的含量。其中，特定的KDC和ADH酶过表达以后，异丁醇含量较5个基因均为过量表达的菌株提升260%；而传统的仅过表达未靶向线粒体的菌株，含量只提升了10%。此外，研究人员建立了另外一种通路，该通路中IVLs过表达并靶向线粒体，KDC过表达并靶向细胞质，异丁醇的含量则在培养基中加入α-KIV后有明显的提高。这说明细胞质中α-KIV的含量是该代谢通路的一个限制因素。
最后，研究人员得出结论将整个异丁醇代谢通路靶向线粒体能够极大的提升支链醇的产量。
Compartmentalization of metabolic pathways in yeast mitochondria improves the production of branched-chain alcohols
José L Avalos, Gerald R Fink & Gregory Stephanopoulos
Efforts to improve the production of a compound of interest in Saccharomyces cerevisiae have mainly involved engineering or overexpression of cytoplasmic enzymes. We show that targeting metabolic pathways to mitochondria can increase production compared with overexpression of the enzymes involved in the same pathways in the cytoplasm. Compartmentalization of the Ehrlich pathway into mitochondria increased isobutanol production by 260%, whereas overexpression of the same pathway in the cytoplasm only improved yields by 10%, compared with a strain overproducing enzymes involved in only the first three steps of the biosynthetic pathway. Subcellular fractionation of engineered strains revealed that targeting the enzymes of the Ehrlich pathway to the mitochondria achieves greater local enzyme concentrations. Other benefits of compartmentalization may include increased availability of intermediates, removing the need to transport intermediates out of the mitochondrion and reducing the loss of intermediates to competing pathways.
