History, Background and General Aspects

Hans Vilter, who revealed the nature of the first representative of the large family of VHPOs, a bromoperoxidase (VBrPO) present in the marine brown alga Ascophyllum nodosum, described the history of his discovery in the following way  

The so-called Soret band, a strong absorption at ca 410 nm, is typical of haeme enzymes. 

The cannulae of Hamilton syringes contain a vanadium-doped steel. 

Organisms containing vanadate-dependent haloperoxidases. The enzymes from the algae A. nodosum and Cor. officinalis and the lichen X parietina are hromoperoxidases, and the fungal enzyme (Cur. inaequalis, shown with sporangia) is a chloroperoxidase. 

The pseudohalide azide inhibits VCIPO. The first stmcturally characterised VHPO had in fact been crystallised in its azide-inhibited form. Inhibition has also been noted with hydroxylamine and hydrazine. Further, structural analogues of vanadate, such as [ALF4] and phosphate, are potent inhibitors. In turn, vanadate inhibits many phosphatases (and other phosphate-metabolising enzymes). On the other hand, apo-VHPOs can exhibit some phosphatase activity, and vanadate-inhibited phosphatases show some haloperoxidase activity. These phenomena will be discussed in Section 5.2.1. 

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