Key Enzymes in the Nitroglycerin Degradation Pathway

Nitroglycerin (NG), widely used in explosives, propellants and pharmaceuticals, can be found in contaminated groundwater and soil and poses potential hazards to the environment. Arthrobacter sp. JBH1 was the first bacterial isolate able to grow on nitroglycerin (NG) as the sole source of carbon and nitrogen. The initial reaction and some of the enzymes involved in the NG transformation pathway were proposed, but the genes that encode the initial enzymes and the mechanism of release of the third nitrate group were unknown. In order to rigorously establish the degradation pathway, four old yellow enzyme (OYE) homologs from the genome of JBH1, and a glycerol kinase homolog, MngP, involved in the lower NG transformation pathway were overexpressed and purified from E. coli. The enzyme assays showed that the old yellow enzyme, PfvA, was 8 times more effective than PfvC in catalyzing the initial step of NG transformation. In addition to 1,2-dinitroglycerin (1,2-DNG), 1,3-DNG was a major denitration product. PfvA could also catalyze the transformation of both DNG isomers to 1-MNG and/or 2-MNG. 1-MNG was then subject to phosphorylation by MngP. Another key finding of this study is that the phosphorylated 1-MNG is a substrate for PfvC, which can catalyze removal of the last nitro group to produce glycerol-3-phosphate that enters central metabolism