Sort by: [ Year  (Asc)]
Maiti BK, Maia LB, Pal K, Pakhira B, Aviles T, Moura I, Pauleta SR, Nunez JL, Rizzi AC, Brondino CD, Sarkar S, Moura JJG. "One electron reduced square planar bis(benzene-1,2-dithiolato) copper dianionic complex and redox switch by O2/HO-." Inorganic Chemistry. 2014;53:12799-12808. AbstractWebsite
Moura I, Maia LB, Pauleta SR, Moura JJG. "A bird’s-eye view of denitrification in relation to the nitrogen cycle." In: Moura I, Moura JJG, Pauleta SR, Maia LB, eds. Metalloenzymes in Denitrification: Applications and Environmental Impacts, RSC Metallobiology Series No. 9 (ISBN: 978-1-78262-376-2). Vol. 39. The Royal Society of Chemistry; 2017:. Abstract

This book is devoted to denitrification, an anaerobic process that is used by a wide range of bacteria for energy generation. The overall process involves nitrate, which is present in soil or water, being reduced to gaseous dinitrogen. This initial chapter aims to place denitrification in the larger context of the nitrogen biogeochemical cycle (a bird’s eye view). Detailed topics are developed through the many following contributions. Denitrification is a landscape for probing the structures, functions and mechanisms of action of a wide range of highly specialised metalloenzymes. These carry out, sequentially, four oxo-transfer reactions: NO3 → NO2˙NO → N2O → N2. The environmental implications of these processes are of particular relevance. Nitrate accumulation and the release of nitrous oxide into the atmosphere due to the excessive use of fertilisers in agriculture are examples of two environmental problems in which denitrification plays a central role.

Maia LB, Moura I, Moura JJG. "EPR spectroscopy on mononuclear molybdenum-containing enzymes." In: Hanson G, Berliner LJ, eds. Future Directions in Metalloprotein and Metalloenzyme Research, Biological Magnetic Resonance, Vol. 33 (ISBN: 978-3-319-59100-1). Vol. 12. Cham: Springer Publishers; 2017:. Abstract

The biological relevance of molybdenum was demonstrated in the early 1950s-1960s, by Bray, Beinert, Lowe, Massey, Palmer, Ehrenberg, Pettersson, Vänngård, Hanson and others, with ground-breaking studies performed, precisely, by electron paramagnetic resonance (EPR) spectroscopy. Those earlier studies, aimed to investigate the mammalian xanthine oxidase and avian sulfite oxidase enzymes, demonstrated the surprising biological reduction of molybdenum to the paramagnetic Mo5+. Since then, EPR spectroscopy, alongside with other spectroscopic methods and X-ray crystallography, has contributed to our present detailed knowledge about the active site structures, catalytic mechanisms and structure/activity relationships of the molybdenum-containing enzymes.
This Chapter will provide a perspective on the contribution that EPR spectroscopy has made to some selected systems. After a brief overview on molybdoenzymes, the Chapter will be focused on the EPR studies of mammalian xanthine oxidase, with a brief account on the prokaryotic aldehyde oxidoreductase, nicotinate dehydrogenase and carbon monoxide dehydrogenase, vertebrate sulfite oxidase, and prokaryotic formate dehydrogenases and nitrate reductases.

Maia LB, Moura JJG. "Lessons from denitrification for the human metabolism of signalling nitric oxide." In: Moura I, Moura JJG, Pauleta SR, Maia LB, eds. Metalloenzymes in Denitrification: Applications and Environmental Impacts, RSC Metallobiology Series No. 9 (ISBN: 978-1-78262-376-2). Vol. 41. The Royal Society of Chemistry; 2017:. Abstract

The nitric oxide radical ˙NO (NO) is a signalling molecule involved in several physiological processes in humans, including vasodilation, immune response, neurotransmission, platelet aggregation, apoptosis and gene expression. Undue normal conditions, NO synthases catalyse the formation of NO from l-arginine and dioxygen. Yet, upon a hypoxic event, when the decreased dioxygen concentration compromises NO synthase activity, cells can generate NO from another source: nitrite. Since the late 1990s, it has become clear that nitrite can be reduced back to NO under hypoxic/anoxic conditions. Simultaneously, it was realised that nitrite can exert a significant cytoprotective action in vivo during ischaemia and other pathological conditions. Presently, blood and tissue nitrite are recognised as NO “storage forms” that can be made available in order to maintain NO formation and ensure cell signalling and survival under challenging conditions. To reduce nitrite to NO, human cells can use different metalloproteins that are present in cells for carrying out other functions, including several haemic proteins and molybdoenzymes, forming what we refer to as “non-dedicated nitrite reductases”. In this chapter, two non-dedicated nitrite reductases—xanthine oxidase and myoglobin—will be described, and the human nitrate/nitrite/NO signalling pathway will be discussed within the cellular context and the nitrogen cycle scenario.

Maia LB, Moura I, Moura JJG. "Molybdenum and tungsten-containing enzymes: an overview." In: Hille R, Schulzke C, Kirk M, eds. Molybdenum and Tungsten Enzymes: Biochemistry, RSC Metallobiology Series No. 5 (ISBN: 978-1-78262-089-1). Vol. 28. The Royal Society of Chemistry; 2017:. Abstract

Molybdenum is essential to most organisms, being found in the active site of enzymes that catalyze redox reactions involving carbon, nitrogen and sulfur atoms of key metabolites. Some of the molybdenum-dependent reactions constitute key steps in the global biogeochemical cycles of carbon, nitrogen and sulfur, with particular emphasis on the atmospheric dinitrogen fixation into ammonium. Presently, more than 50 molybdoenzymes are known. The great majority are prokaryotic, with eukaryotes holding only a restricted number of molybdoenzymes. Tungsten, probably because of its limited bioavailability, is less used, being found most often in anaerobic thermophilic prokaryotes.

This chapter provides an overview on the molybdo- and tungstoenzymes.
Their physiological context and significance will be described in Section 1.2,where the recent hypothesis that the lack of molybdenum could have been the limiting factor for the life evolution and expansion on early Earth will receive special attention (Section 1.2.1). A brief introduction to the chemical properties that shape the catalytically competent molybdenum/tungsten centres will be made in Section 1.3. In Section 1.4, the enzymes will be grouped in five main families (Sections 1.4.1 to 1.4.5), according to their metal/cofactor structure, and a general view on the structural (section (a)) and mechanistic (section (b)) versatility of each family will be presented. A brief account of novel heteronuclear centres containing molybdenum, whose physiological function is not yet fully understood, will be made in Section 1.4.6. A final outlook on our present knowledge about these enzymes will conclude this chapter.