Periplasmic nitrate reductases and formate dehydrogenases: Biological control of the chemical properties of Mo and W for fine tuning of reactivity, substrate specificity and metabolic role

► Structural, spectroscopic and biochemical features of Naps and Fdhs were revised. ► Several catalytic mechanism proposals of Naps and Fdhs were reviewed and compared. ► The physiological roles of Naps and Fdhs in different organisms were discussed. ► Mo and W uptake and cofactor biosynthesis in Bacteria (Escherichia coli and Desulfovibrio) was analyzed. ► Use of Mo or W in DMSO reductases, Fdhs and Naps was reviewed.