Vanadium
With an average concentration of 35 nM, vanadium (V) (essentially present in the form of ion pairs Na+H2VO4-) is the second-to-most abundant transition metal in seawater, outclassed only by molybdenum (present as molybate MoO42-, ca. 100 nM). Vanadate-dependent haloperoxidases (VHPOs) can be present in marine brown, green, and red, algae, in (symbiotic) marine cyanobacteria, in Streptomyces bacteria, and in terrestrial fungi and lichen. Since the discovery of the first representative of these haloperoxidases and the bromoperoxidase VBrPo of the brown algae Ascophyllum nodosum, also known as wrack or pigweed, a plethora of macroalgae has been reported to have available VHPOs hence haloperoxidases that contain vanadate H2VO4- coordinated to a histidine residue in the enzyme's active center, and thus clearly distinct from the more common heme- based and non-heme peroxidases.