Reduction of a heme cofactor initiates N-nitroglycine degradation by NnlA

Abstract

The NnlA enzyme from Variovorax sp. strain JS1663 degrades the linear nitramine N-23 nitroglycine (NNG)—a natural product produced by some bacteria—to glyoxylate and nitrite 24 (NO2–). Ammonium (NH4+) was predicted as the third product of this reaction. A source of non-25 heme FeII was shown to be required for initiation of NnlA activity. However, it was unclear if 26 this FeII was being used as a metallocofactor or a reductant. This study reveals that NnlA 27 contains a b-type heme cofactor. Reduction of this heme is required to initiate NnlA activity. 28 Reduction can occur either by addition of a non-heme FeII source or by reduction with dithionite. 29 Therefore, FeII is not an essential substrate for holoenzyme activity.