Fig. (2).

Schematic view of a theoretically thinkable activation mechanism of a vanadium-based insulinomimetic drug. The idea was adopted from [37] and [122]. It is assumed that the PTP1B enzyme is the key target to treat diabetes effectively. This negative regulator of the glucose cell uptake can be inactivated by vanadate (V) which is strongly attached to the sulfide (deprotonated sulfhydryl) head group of the sidechain of cystein 215 at the catalytic site. In consequence, agonistic phosphate cannot access the same site because vanadate is the stronger competitive binder. Now, that PTP1B has been deactivated, the enzyme is kept in the phosphorylated state, thereby maintaining alive the signal transduction and glucose continues entering the cells as if more insulin was working through the insulin receptors. This is the clinically observed insulin-mimetic or enhancing effect. Vanadyl compounds BEOV or BMOV are converted into vanadate anions through speciation, a sort of prodrug conversion [122].