A mechanistic rationalisation for the substrate specificity of recombinant mammalian 4-hydroxyphenylpyruvate dioxygenase (4-HPPD)

Article abstract of DOI:10.1016/S0040-4020(97)00398-0

The isolation and purification of α-ketoisocaproate dioxygenase [α-KICD] from rat liver is described. Sequence determination of the purified protein revealed it to have complete homology to rat liver 4-hydroxyphenylpyruvate dioxygenase [4-HPPD] which was confirmed by the cloning and expression of the gene encoding 4-HPPD in E. coli. Examination of the substrate specificity of the resulting soluble recombinant protein revealed it to be capable of the oxidative decarboxylation of a range of ketoacids derived from proteinogenic amino acids. The significance of the turnover of these different ketoacids is discussed in relation to the mechanism of this fascinating enzyme.