Partial identity of the 2-oxoglutarate and ascorbate binding sites of prolyl 4-hydroxylase.

摘要: Abstract Various hydroxybenzenes, hydroxybenzoic acids, and related compounds resemble structurally both 2-oxoglutarate ascorbate, two reactants needed in the reaction of prolyl 4-hydroxylase. These substances were found to inhibit 4-hydroxylase competitively with respect cosubstrates. Ortho-dihydroxy derivatives, which are capable chelating enzyme-bound iron, most effective inhibitors, Ki values about 5 microM. In contrast, pyridine 2-carboxylates, have previously been reported enzyme 2-oxoglutarate, it uncompetitively ascorbate. a separate set experiments side chain ascorbate molecule was shown make no significant contribution binding reductant enzyme, as D(-)-isoascorbate 5,6-O-isopropylidene gave essentially same Vmax Km On other hand, structural modifications ring atoms that abolished capacity destroyed cosubstrate inhibitory activity, L-galactono gamma-lactone. The site therefore appears consist cis-positioned coordination sites iron is thus partially identical 2-oxoglutarate. This mode interaction suggests reduces through an "inner-sphere" mechanism. inhibitors studied appear react at different phases catalytic cycle, determined by oxidation state atom.