Expression and Post‐translational Modification of Human 4‐hydroxy‐phenylpyruvate Dioxygenase

Abstract

4-hydroxyphenylpyruvate dioxygenase (HPD) (EC 1.13.11.27) is a key enzyme involved in tyrosine catabolism. Congenital HPD deficiency is a rare, relatively benign condition known as hereditary type III tyrosinemia. The severe type I tyrosinemia, caused by a deficiency of fumarylacetoacetate hydrolase which functions downstream of HPD in the tyrosine degradation pathway, is often associated with decreased expression of HPD, and interestingly, inhibition of HPD activity seems to ameliorate the clinical symptoms of type I tyrosinemia. The HPD gene was previously mapped to the chromosomal region 12q24-->qter. In the present study high-resolution chromosome mapping localized the HPD gene to 12q24.31. DNase I footprinting, revealed that four regions of the HPD promoter were protected by rat liver nuclear proteins. Computer-assisted analyses suggested that these elements might bind Sp1/AP2, HNF4, HNF3/CREB, and C/EBP, respectively. In transient transfection experiments, the proximal 271bp of the promoter conferred basal transcriptional activation in human Chang cells. Sequences in intron 1 were able to enhance the activity of this basal promoter. Finally, vaccinia virus-based expression provided evidence that HPD is subject to phosphorylation, and furthermore, allowed mapping of the HPD protein in the human keratinocyte 2D database.

The transcriptional activity of hepatocyte nuclear factor 4 alpha is inhibited via phosphorylation by ERK1/2

“…The other genes we have selected are also implicated in metabolism. 4-Hydroxyphenyl pyruvate dioxygenase (HPD) is an enzyme participating in tyrosine metabolism [ 32 ]. Mutations of the gene lead to a benign Mendelian disorder called Tyrosinaemia (type III).…”

Zinc adaptation and resistance to cadmium toxicity in mammalian cells: Molecular insight by proteomic analysis

“…Indeed, regulation of the balance between the two activities of this moonlighting protein is not elucidated, and the physiological meaning of the enzymatic reaction has been questioned [58]. Yet, from what is known about regulation of enzymes involved in tyrosine turnover, including HPPD [55], it is beyond doubt that signaling pathways regulate flow between the different metabolic routes available for tyrosine. In this respect, disruption of calcium homeostasis by thapsigargin in HZR cells, and its consequences on signaling pathways, strongly impacts the resistance of these cells against cadmium (Fig.…”

Tissue distribution, intracellular localization and proteolytic processing of rat 4‐hydroxyphenylpyruvate dioxygenase

“…A surface probability plot indicates that this site would be accessible on the surface of all HPDs. By using adenoviral based expression of human HPD we have obtained evidence that HPD is subject to phosphorylation in cell cultures (Aarenstrup et al, 2002). However, whether this phosphorylation is of biological significance and targets serine 249 remain to be established.…”

“…As described above significant levels of HPD mRNA and HPD immunoreactivity were detected in neurons, a finding apparently in conflict with the noted absence of HPD enzymatic activity in the brain. Analysis of the exon-intron organization of the human HPD gene (Aarenstrup et al, 2002;Rü etschi et al, 1997) reveals that exon-skipping with maintenance of the reading frame is possible for most exons except for exons 5, 6, 8, and 10. Given the conservation of the HPD protein during evolution it is conceivable that the rat HPD shares the same exon-intron organization.…”