Structure Diversity of Nitric Oxide Synthases (NOS): The Emergence of New Forms in Photosynthetic Organisms

CORREA-ARAGUNDE N; FORESI N; LAMATTINA L

Frontiers in Plant Physiology

Frontiers

Año: 2013 vol. 4 p. 232 - 235

1664-462X

Humans have dramatically increased the level of nitrogen (N) circulating in the troposphere and the earth surface during the last century, correlating with the population increase. As an undesirable consequence, high levels of reactive N are polluting the environment where humans inhabit. Nitric oxide (NO) is one of the reactive N species with both positive and negative impact on life. NO synthases (NOS) are enzymes that oxidize arginine to citrulline and generate the denitrifying intermediate NO which can be subsequently reduced to N2O and N2. NOS are large modular enzymes present in all kingdoms of life that are evolving rapidly and independently. A recently described NOS from the marine unicellular microalgae Ostreococcus tauri, belonging to the picoplankton in oceans, adds new insights to study the evolution of the complex organization of these enzymes. In this opinion we discuss the structure and diversity of the emerging new NOS forms described in prokaryotes and eukaryotes. Regarding the controversy about the existence of canonical NOS in higher plants, we propose that the latest findings support the existence of a high diversity of NOS forms in different lineages. Thereby, since higher plant species whose genomes have been fully sequenced are still scarce, it cannot be discarded that a new form of NOS may be evolved in higher plants.