The 2-oxoglutarate binding site of prolyl 4-hydroxylase. Identification of distinct subsites and evidence for 2-oxoglutarate decarboxylation in a ligand reaction at the enzyme-bound ferrous ion.

The structure and function of the 2-oxoglutarate binding site of prolyl 4-hydroxylase was studied by assaying the inhibitory potential of 24 selected aliphatic or aromatic compounds. All except one of them inhibited the enzyme competitively with respect to 2-oxoglutarate and noncompetitively with respect to Fe2+, the Ki values ranging from 0.8 microM to over 15 mM. The Ki values for the two most effective inhibitors, pyridine 2,5-dicarboxylate and 2,4-dicarboxylate, were about 0.8 microM and 2 microM, these compounds being the most potent inhibitors of prolyl 4-hydroxylase with respect to 2-oxoglutarate known so far. Only one of the compounds tested, 2-oxoadipinate, was able to support hydr…