Williams Shoshana C, Austin Rachel Narehood
Department of Chemistry, Stanford University, Stanford, CA, United States.
Department of Chemistry, Barnard College, Columbia University, New York City, NY, United States.
Front Microbiol. 2022 Feb 28;13:845551. doi: 10.3389/fmicb.2022.845551. eCollection 2022.
Alkane-oxidizing enzymes play an important role in the global carbon cycle. Alkane monooxygenase (AlkB) oxidizes most of the medium-chain length alkanes in the environment. The first AlkB identified was from GPo1 (initially known as ) in the early 1970s, and it continues to be the family member about which the most is known. This AlkB is found as part of the OCT operon, in which all of the key proteins required for growth on alkanes are present. The AlkB catalytic cycle requires that the diiron active site be reduced. In GPo1, electrons originate from NADH and arrive at AlkB the intermediacy of a flavin reductase and an iron-sulfur protein (a rubredoxin). In this Mini Review, we will review what is known about the canonical arrangement of electron-transfer proteins that activate AlkB and, more importantly, point to several other arrangements that are possible. These other arrangements include the presence of a simpler rubredoxin than what is found in the canonical arrangement, as well as two other classes of AlkBs with fused electron-transfer partners. In one class, a rubredoxin is fused to the hydroxylase and in another less well-explored class, a ferredoxin reductase and a ferredoxin are fused to the hydroxylase. We review what is known about the biochemistry of these electron-transfer proteins, speculate on the biological significance of this diversity, and point to key questions for future research.
烷烃氧化酶在全球碳循环中发挥着重要作用。烷烃单加氧酶（AlkB）可氧化环境中大部分中等链长的烷烃。20世纪70年代初首次鉴定出的AlkB来自GPo1（最初称为），它仍然是人们了解最多的家族成员。这种AlkB是OCT操纵子的一部分，在该操纵子中存在烷烃生长所需的所有关键蛋白质。AlkB催化循环要求二铁活性位点被还原。在GPo1中，电子源自NADH，并通过黄素还原酶和铁硫蛋白（一种红素氧还蛋白）的介导到达AlkB。在本小型综述中，我们将回顾关于激活AlkB的电子传递蛋白的经典排列方式的已知信息，更重要的是，指出其他几种可能的排列方式。这些其他排列方式包括存在一种比经典排列中更简单的红素氧还蛋白，以及另外两类带有融合电子传递伴侣的AlkB。在一类中，一种红素氧还蛋白与羟化酶融合，而在另一类较少被探索的情况中，一种铁氧还蛋白还原酶和一种铁氧还蛋白与羟化酶融合。我们回顾了关于这些电子传递蛋白生物化学的已知信息，推测了这种多样性的生物学意义，并指出了未来研究的关键问题。
