Structure, mechanism and function in the ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) superfamily

D-核酮糖1，5-二磷酸羧化酶/加氧酶（RubisCO）是生物圈中最丰富的酶之一，催化地球上主要的CO2固定过程--卡尔文循环的关键反应。RubisCO超家族包括四种不同类型的蛋白质。I、II和III型RubisCO是真正的CO2固定酶，分别在植物（I型）、细菌（I型和II型）和古细菌（III型）中起作用。与此相反，IV型蛋白（细菌）缺少羧化反应所必需的残基，因此缺乏固定CO2的能力。这些“Rubisco样蛋白质”（RLP）分为六个不同的分支，预期催化不同的反应。本研究旨在鉴定不同进化枝的RLP催化的反应，并破译其生物学功能。将采用结构和生物化学相结合的方法来研究单个RLP的底物和反应特异性。RLP的生理作用将通过细胞提取物实验和可能揭示新代谢途径的诱变研究进行测试。RubisCO超家族内催化功能的多样化将通过结构研究和定点诱变来研究，以修改并将“新”功能引入酶支架中。这项研究的结果可能会扩展我们对这个重要的酶超家族的生物学意义的认识，以及对其单个成员催化的反应的进化和多样化的认识。这也可能与RubisCO的（农业上重要的）工程或生物技术上适用的羧化酶的开发有关。

D-Ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) is one of the most abundant en-zymes in the biosphere and catalyzes the key reaction of the Calvin cycle, the major process of CO2-fixation on earth. The RubisCO superfamily includes four distinct types of proteins. TYPE I, II and III RubisCOs are true CO2-fixing enzymes that operate in plants (TYPE I), bacteria (TYPE I and II), and archaea (TYPE III), respectively. In contrast to that, TYPE IV proteins (bacterial) miss residues essen-tial for a carboxylation reaction and consequently lack the ability to fix CO2. These “RUBISCO-LIKE PROTEINS” (RLP) fall into six divergent clades that are expected to catalyze different reactions. This study aims at identifying the reactions catalyzed by RLPs of different clades and deciphering their biological function. A combined approach of structural and biochemical methods will be used to ex-plore the substrate and reaction specificity of individual RLPs. The physiological role of RLPs will be tested by cell extract experiments and mutagenic studies that may unravel novel metabolic pathways. The diversification of catalytical functions within the RubisCO superfamily will be investigated by structural studies and site directed mutagenesis to modify and to introduce “novel” functions into the enzyme scaffold. The results of this study may extend our knowledge on the biological significance of this important superfamily of enzymes, as well as on the evolution and diversification of the reactions catalyzed by its single members. This might also be of relevance for an (agriculturally important) engineering of RubisCO, or the development of biotechnologically applicable carboxylases.