Mechanism of alkane formation by cyanobacterial aldehyde decarbonylase

在这个化学部生命过程化学奖中，E。来自密歇根大学的Neil Marsh将阐明一种新发现的来自蓝藻的碳氢化合物形成酶-醛脱羧酶（cAD）的机制。生物合成途径，产生碳氢化合物已成为最近的强烈兴趣的主题，因为他们的潜力，以产生新的生物燃料已被确认。 醛脱羰酶是一类研究充分的酶，非血红素二铁加氧酶的成员。 初步研究表明，cAD催化一个最不寻常的反应，涉及长链脂肪醛转化为相应的烷烃和甲酸酯。 为了研究该机制，将合成可能作为基于机制的抑制剂的替代底物，以获得反应中拟议的自由基中间体的证据。 还原系统在反应中的作用将被研究，并将确定宿主蓝藻P. marinus中天然还原系统的组分。定点诱变将用于研究活性位点残基在确定底物特异性和控制反应机制中的作用。 最后，动力学同位素效应将被测量，以提供深入了解cAD的速率决定步骤和过渡态的性质，导致碳-碳键cript.There是一个迫切需要开发新的途径，以生产生物燃料的基础上，碳氢化合物作为可持续的替代化石燃料。 蓝藻酶醛脱羰酶产生碳氢化合物，并吸引了生物燃料应用的特别兴趣，但其极低的活性提出了一个主要的绊脚石，其使用。 了解酶的工作原理是设计更好的酶或合成催化剂的第一步，这些酶或催化剂可以更有效地合成碳氢化合物。 反过来，这可能会允许开发新的生物燃料路线，以取代目前的化石燃料，包括汽油，柴油和喷气燃料。

In this award from the Chemistry of Life Processes in the Chemistry Division, Dr. E. Neil Marsh, from the University of Michigan, will elucidate the mechanism of a newly-discovered hydrocarbon-forming enzyme from cyanobacteria, aldehyde decarbonylase (cAD). Biosynthetic pathways that generate hydrocarbons have become the subject of intense interest recently as their potential to generate new biofuels has been recognized. Aldehyde decarbonylase is a member of a well-studied class of enzymes, the non-heme di-iron dioxygenases. Preliminary studies have shown that cAD catalyzes a most unusual reaction involving the conversion of long-chain fatty aldehydes to the corresponding alkanes and formate. To investigate the mechanism, alternative substrates that may act as mechanism-based inhibitors will be synthesized to gain evidence for proposed radical intermediates in the reaction. The role of the reducing system in the reaction will be investigated and the components of the native reducing system in the host cyanobacterium P. marinus, will be identified. Site-directed mutagenesis will be used to investigate the role of active site residues in determining substrate specificity and controlling the mechanism of the reaction. Lastly, kinetic isotope effects will be measured to provide insight into the rate determining step in cAD and the nature of the transition state leading to carbon-carbon bond cleavage.There is a pressing need to develop new pathways to produce biofuels based on hydrocarbons as sustainable alternatives to fossil fuels. The cyanobacterial enzyme aldehyde decarbonylase produces hydrocarbons and has attracted particular interest for biofuels applications; yet its extremely low activity presents a major stumbling block to its use. Understanding how the enzyme works is the first step to designing better enzymes, or synthetic catalysts, that accomplish the synthesis of hydrocarbons more efficiently. This, in turn, may allow the development of new routes to biofuels that can substitute for current fossil fuels including gasoline, diesel and jet fuels.