Enzymatic evidence that the natural product N-nitroglycine is degraded by diverse bacteria

Submitting author affiliation:
University of Central Florida, Orlando, United States

Beilstein Arch. 2023, 202363. https://doi.org/10.3762/bxiv.2023.63.v1

Published 19 Dec 2023

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Linear nitramines (R-N(R′)NO2; R′ = H or alkyl) are toxic compounds, some with environmental relevance while others are rare natural product nitramines. One of these natural product nitramines is N-nitroglycine (NNG) is produced by some Streptomyces strains and exhibits antibiotic activity towards Gram-negative bacteria. An NNG degrading heme enzyme, called NnlA, has recently been discovered in the genome of Variovorax sp. Strain JS1663 (Vs NnlA). Evidence is presented that NnlA and therefore, NNG degradation activity is widespread. To achieve this objective, we tested characterized and tested the NNG degradation activity of five Vs NnlA homologs originating from bacteria spanning several classes and isolated from geographically distinct locations. E. coli transformants containing all five homologs converted NNG to nitrite. Four of these five homologs were isolated and characterized. Each isolated homolog exhibited similar oligomerization and heme occupancy as Vs NnlA. Reduction of this heme was shown to be required for NnlA activity in each homolog, and each homolog degraded NNG to glyoxylate, NO2 and NH4+ in accordance with observations of Vs NnlA. It was also shown that NnlA cannot degrade the NNG analog 2-nitroaminoethanol. The combined data strongly suggest that NnlA enzymes specifically degrade NNG and are found in diverse bacteria and environments. These results imply that NNG is also produced in diverse environments and NnlA may act as a detoxification enzyme to protect bacteria from exposure to NNG.

Keywords: Nitramine; N-N bond; natural products; enzymology

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Strickland, K. A.; Martinez Rodriguez, B.; Holland, A. A.; Wagner, S.; Luna-Alva, M.; Graham, D. E.; Caranto, J. D. Beilstein Arch. 2023, 202363. doi:10.3762/bxiv.2023.63.v1

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