4-hydroxyphenylpyruvate dioxygenase
| 4-hydroxyphenylpyruvate dioxygenase | |||||||||
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Homodimer of 4-Hydroxyphenylpyruvate dioxygenase. Red ribbon represents iron-containing catalytic domain (with Fe 2+ represented as red-orange spheres); blue represents the oligomeric domain. Image generated from published structural data
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| Identifiers | |||||||||
| EC number | 1.13.11.27 | ||||||||
| CAS number | 9029-72-5 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / EGO | ||||||||
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| Search | |
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| PMC | articles |
| PubMed | articles |
| NCBI | proteins |
| 4-hydroxyphenylpyruvate dioxygenase | |
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| Identifiers | |
| Symbol | HPPD |
| Alt. symbols | HPD; PPD |
| Entrez | 3242 |
| HUGO | 5147 |
| OMIM | 609695 |
| RefSeq | NM_002150 |
| UniProt | P32754 |
| Other data | |
| EC number | 1.13.11.27 |
| Locus | Chr. 12 q24-qter |
4-Hydroxyphenylpyruvate dioxygenase (HPPD), also known as α-ketoisocaproate dioxygenase (KIC dioxygenase), is an Fe(II)-containing non-heme oxygenase that catalyzes the second reaction in the catabolism of tyrosine - the conversion of 4-hydroxyphenylpyruvate into homogentisate. HPPD also catalyzes the conversion of phenylpyruvate to 2-hydroxyphenylacetate and the conversion of α-ketoisocaproate to β-hydroxy β-methylbutyrate. HPPD is an enzyme that is found in nearly all aerobic forms of life.
HPPD is categorized within a class of oxygenase enzymes that usually utilize α-ketoglutarate and diatomic oxygen to oxygenate or oxidize a target molecule. However, HPPD differs from most molecules in this class due to the fact that it does not use α-ketoglutarate, and it only utilizes two substrates while adding both atoms of diatomic oxygen into the product, homogentisate. The HPPD reaction occurs through a NIH shift and involves the oxidative decarboxylation of an α-oxo acid as well as aromatic ring hydroxylation. The NIH-shift, which has been demonstrated through isotope-labeling studies, involves migration of an alkyl group to form a more stable carbocation. The shift, accounts for the observation that C3 is bonded to C4 in 4-hydroxyphenylpyruvate but to C5 in homogentisate. The predicted mechanism of HPPD can be seen in the following figure:
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