Medina Michael, Rizo Antonia, Dinh David, Chau Briana, Omidvar Moussa, Juarez Andrew, Ngo Julia, Johnson Hope A
Department of Biological Science, Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, CA, United States.
Front Microbiol. 2018 Nov 13;9:2671. doi: 10.3389/fmicb.2018.02671. eCollection 2018.
Bacterial manganese (Mn) oxidation is catalyzed by a diverse group of microbes and can affect the fate of other elements in the environment. Yet, we understand little about the enzymes that catalyze this reaction. The Mn oxidizing protein MopA, from sp. strain SD-21, is a heme peroxidase capable of Mn(II) oxidation. Unlike Mn oxidizing multicopper oxidase enzymes, an understanding of MopA is very limited. Sequence analysis indicates that MopA contains an N-terminal heme peroxidase domain and a C-terminal calcium binding domain. Heterologous expression and nickel affinity chromatography purification of the N-terminal peroxidase domain (MopA-hp) from sp. strain SD-21 led to partial purification. MopA-hp is a heme binding protein that requires heme, NAD, and calcium (Ca) for activity. Mn oxidation is also stimulated by the presence of pyrroloquinoline quinone. MopA-hp has a for Mn(II) of 154 ± 46 μM and = 1.6 min. Although oxygen requiring MopA-hp is homologous to peroxidases based on sequence, addition of hydrogen peroxide and hydrogen peroxide scavengers had little effect on Mn oxidation, suggesting this is not the oxidizing agent. These studies provide insight into the mechanism by which MopA oxidizes Mn.
多种微生物可催化细菌锰（Mn）氧化，且该过程会影响环境中其他元素的归宿。然而，我们对催化此反应的酶了解甚少。来自菌株SD - 21的锰氧化蛋白MopA是一种能够氧化Mn（II）的血红素过氧化物酶。与锰氧化多铜氧化酶不同，对MopA的了解非常有限。序列分析表明，MopA包含一个N端血红素过氧化物酶结构域和一个C端钙结合结构域。对来自菌株SD - 21的N端过氧化物酶结构域（MopA - hp）进行异源表达和镍亲和层析纯化，得到了部分纯化产物。MopA - hp是一种血红素结合蛋白，其活性需要血红素、NAD和钙（Ca）。吡咯喹啉醌的存在也能刺激锰的氧化。MopA - hp对Mn（II）的Km为154±46μM且kcat = 1.6分钟。尽管基于序列，需氧的MopA - hp与过氧化物酶同源，但添加过氧化氢和过氧化氢清除剂对锰氧化的影响很小，这表明过氧化氢不是氧化剂。这些研究为MopA氧化锰的机制提供了见解。
