From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
From the Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
J Biol Chem. 2018 Dec 21;293(51):19909-19918. doi: 10.1074/jbc.RA118.005485. Epub 2018 Oct 25.
Bacterial microcompartments encapsulate enzymatic pathways that generate small, volatile, aldehyde intermediates. The and microcompartment (RMM) operon from encodes four enzymes, including ()-1-amino-2-propanol dehydrogenase and a likely propionaldehyde dehydrogenase. We show here that a third enzyme (and its nonmicrocompartment-associated paralog) is a moderately specific ()-1-amino-2-propanol kinase. We determined the structure of apo-aminopropanol kinase at 1.35 Å, revealing that it has structural similarity to hexosamine kinases, choline kinases, and aminoglycoside phosphotransferases. We modeled substrate binding, and tested our model by characterizing key enzyme variants. Bioinformatics analysis established that this enzyme is widespread in Actinobacteria, Proteobacteria, and Firmicutes, and is very commonly associated with a candidate phospholyase. In Rhizobia, aminopropanol kinase is generally associated with aromatic degradation pathways. In the RMM (and the parallel pathway that includes the second paralog), aminopropanol kinase likely degrades aminoacetone through a propanolamine-phosphate phospho-lyase-dependent pathway. These enzymatic activities were originally described in , but the proteins responsible have not been previously identified. Bacterial microcompartments typically co-encapsulate enzymes which can regenerate required co-factors, but the RMM enzymes require four biochemically distinct co-factors with no overlap. This suggests that either the RMM shell can uniquely transport multiple co-factors in stoichiometric quantities, or that all enzymes except the phospho-lyase reside outside of the shell. In summary, aminopropanol kinase is a novel enzyme found in diverse bacteria and multiple metabolic pathways; its presence in the RMM implies that this microcompartment degrades aminoacetone, using a pathway that appears to violate some established precepts as to how microcompartments function.
细菌微室将产生小的、挥发性醛中间产物的酶途径包裹起来。来自 的 和 微室 (RMM) 操纵子编码四个酶，包括 ()-1-氨基-2-丙醇脱氢酶和可能的丙醛脱氢酶。我们在这里表明，第三种酶（及其非微室相关的旁系同源物）是一种中度特异性的 ()-1-氨基-2-丙醇激酶。我们在 1.35 Å 处确定了脱辅基氨基丙醇激酶的结构，揭示其与己糖胺激酶、胆碱激酶和氨基糖苷磷酸转移酶具有结构相似性。我们模拟了底物结合，并通过表征关键酶变体来测试我们的模型。生物信息学分析表明，这种酶在放线菌、变形菌和厚壁菌门中广泛存在，并且非常常见于候选磷酸裂解酶。在根瘤菌中，氨基丙醇激酶通常与芳香族降解途径有关。在 RMM（和包括第二个旁系同源物的平行途径）中，氨基丙醇激酶可能通过丙醇胺磷酸磷酸裂解酶依赖性途径降解氨基丙酮。这些酶活性最初在 中描述，但以前没有鉴定出负责这些蛋白的酶。细菌微室通常共同包裹可以再生所需辅因子的酶，但 RMM 酶需要四个生化上不同的辅因子，没有重叠。这表明 RMM 壳可以以化学计量的数量独特地运输多种辅因子，或者除磷酸裂解酶外，所有酶都位于壳外。总之，氨基丙醇激酶是一种在多种细菌和多种代谢途径中发现的新型酶；它在 RMM 中的存在表明，这个微室降解氨基丙酮，使用的途径似乎违反了一些关于微室如何发挥作用的既定原则。
