【艾爾】評論

The hydroxylation of specific Pro residues in procollagen, the precursor of collagen, requires the action of the -ketoglutarate-dependent enzyme prolyl 4-hydroxylase. In the normal prolyl 4-hydroxylase reaction, one molecule of  alpha- ketoglutarate and one of bind to the enzyme. The -ketoglutarate is oxidatively decarboxylated to form and succinate. The remaining oxygen atom is then used to hydroxylate an appropriate Pro residue in procollagen. No ascorbate is needed in this reaction. However, prolyl 4-hydroxylase also catalyzes an oxidative decarboxylation of -ketoglutarate that is not coupled to proline hydroxylation. During this reaction, the becomes oxidized, inactivating the enzyme and preventing the proline hydroxylation. Ascorbate is needed to reduce the iron and restore enzyme activity so that proline hydroxylation of procollagen can continue.