Frm2 subgroup enzymes have hypothesized roles in fatty acid signaling pathways and oxidative stress. Frm2 (Saccharomyces cerevisae) shows 4-nitroquinoline-N-oxide (4-NQO) reductase activity (with NADH). CinD (YtjD) is a Lactococcus sp. enzyme that is copper inducible; a knockout mutant of cinD was more sensitive to oxidative stress exerted by 4-nitroquinoline-N-oxide and copper.
Bang, S.Y. et al.
Confirmation of Frm2 as a novel nitroreductase in Saccharomyces cerevisiae.
▸ Abstract
Nitroreductases comprise a group of FMN- or FAD-dependent enzymes that reduce nitrosubstituted compounds by using NAD(P)H, and are found in bacterial species and yeast. Although there is little information on the biological functions of nitroreductases, some studies suggest their possible involvement in oxidative stress responses. In the yeast Saccharomyces cerevisiae, a putative nitroreductase protein, Frm2, has been identified based on its sequence similarity with known bacterial nitroreductases. Frm2 has been reported to function in the lipid signaling pathway. To study the functions of Frm2, we measured the nitroreductase activity of purified Frm2 on 4-nitroquinoline-N-oxide (4-NQO) using NADH. LC-MS analysis of the reaction products revealed that Frm2 reduced NQO into 4-aminoquinoline-N-oxide (4-AQO) via 4-hydroxyaminoquinoline (4-HAQO). An Frm2 deletion mutant exhibited growth inhibition in the presence of 4-NQO. Thus, in this study, we demonstrate a novel nitroreductase activity of Frm2 and its involvement in the oxidative stress defense system.
Biochem Biophys Res Commun.
2012;None(423):638-641
| PubMed ID:
22687599
Mermod, M. et al.
Structure and function of CinD (YtjD) of Lactococcus lactis, a copper-induced nitroreductase involved in defense against oxidative stress.
▸ Abstract
In Lactococcus lactis IL1403, 14 genes are under the control of the copper-inducible CopR repressor. This so-called CopR regulon encompasses the CopR regulator, two putative CPx-type copper ATPases, a copper chaperone, and 10 additional genes of unknown function. We addressed here the function of one of these genes, ytjD, which we renamed cinD (copper-induced nitroreductase). Copper, cadmium, and silver induced cinD in vivo, as shown by real-time quantitative PCR. A knockout mutant of cinD was more sensitive to oxidative stress exerted by 4-nitroquinoline-N-oxide and copper. Purified CinD is a flavoprotein and reduced 2,6-dichlorophenolindophenol and 4-nitroquinoline-N-oxide with k(cat) values of 27 and 11 s(-1), respectively, using NADH as a reductant. CinD also exhibited significant catalase activity in vitro. The X-ray structure of CinD was resolved at 1.35 A and resembles those of other nitroreductases. CinD is thus a nitroreductase which can protect L. lactis against oxidative stress that could be exerted by nitroaromatic compounds and copper.
Journal of Bacteriology
2010;None(192):4172-4180
| PubMed ID:
20562311
