Shandong Provincial Key Laboratory of Applied Mycology, College of Life Sciences, Qingdao Agricultural University, Qingdao, China.
College of Marine Life Science, Ocean University of China, Qingdao, China.
Sci Rep. 2019 Mar 6;9(1):3647. doi: 10.1038/s41598-019-40199-0.
A novel Alcaligenes sp. strain P156, which can utilize nicotinamide as its sole source of carbon, nitrogen and energy, was enriched and isolated from soil in a solid waste treatment plant. Aerobic growth and degradation with nicotinamide were characterized. Seven nicotinamide degradation-related genes were obtained by sequence alignment from the genome sequence of strain P156. Four genes, designated naaA, naaD, naaE and naaF, were cloned and heterologously expressed. Nicotinamide degradation is initiated by deamination to form nicotinic acid catalyzed by the nicotinamidase NaaA, which shares highest amino acid sequence identity (27.2%) with nicotinamidase from Arabidopsis thaliana. Nicotinic acid is converted to 6-hydroxynicotinic acid, which is further oxidized to 2,5-dihydroxypyridine (2,5-DHP). 2,5-DHP is then transformed to a ring-cleavage product, N-formylmaleamic acid, by an Fe dependent dioxygenase NaaD. N-formylmaleamic acid is transformed to fumaric acid through maleamic acid and maleic acid by NaaE and NaaF, respectively. To our knowledge, this is the first report of the complete microbial degradation of nicotinamide in bacteria. Nicotinamide is considered as a model compound for the study of microbial degradation of pyridinic compounds, and the nicotinamide degrading related genes in strain P156 were distributed differently from the reported similar gene clusters. Therefore, this study contribute to the knowledge on the degradation of pyridinic compounds.
一株能以烟酰胺作为唯一碳源、氮源和能源的新型产碱杆菌（Alcaligenes sp.）菌株 P156，是从固体废物处理厂的土壤中富集和分离得到的。对其好氧生长和烟酰胺降解特性进行了研究。通过对 P156 基因组序列的序列比对，获得了 7 个与烟酰胺降解相关的基因。克隆并异源表达了其中的 4 个基因，命名为 naaA、naaD、naaE 和 naaF。烟酰胺的降解是由烟酰胺酶 NaaA 催化脱氨形成烟酸起始的，NaaA 与拟南芥中的烟酰胺酶具有最高的氨基酸序列同一性（27.2%）。烟酸转化为 6-羟基烟酸，进一步氧化为 2,5-二羟基吡啶（2,5-DHP）。2,5-DHP 然后被依赖铁的双加氧酶 NaaD 转化为环裂解产物 N-甲酰基马来酸。N-甲酰基马来酸通过 NaaE 和 NaaF 分别转化为马来酸和富马酸。据我们所知，这是细菌中烟酰胺完全微生物降解的首次报道。烟酰胺被认为是研究吡啶类化合物微生物降解的模型化合物，而 P156 中的烟酰胺降解相关基因的分布与报道的类似基因簇不同。因此，本研究有助于了解吡啶类化合物的降解。
