this hydrogen (H6 or H7) transfers to O15 and in turn the proton transfers from O15 to O16 to O53 to Asp292. This series of proton transfers should have the effect of deactivating the vanadate since the first step of the mechanism is thought to involve dissociation of diprotonated O4 from vanadate and subsequent bonding of vanadate with H2O2 (Scheme 2).