Proline oxidase

Last updated
PRODH
Identifiers
Aliases PRODH , HSPOX2, PIG6, POX, PRODH1, PRODH2, TP53I6, Proline oxidase, proline dehydrogenase 1
External IDs OMIM: 606810 MGI: 97770 HomoloGene: 40764 GeneCards: PRODH
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_001195226
NM_016335

NM_011172

RefSeq (protein)

NP_001182155
NP_057419

NP_035302

Location (UCSC) Chr 22: 18.91 – 18.94 Mb Chr 16: 17.88 – 17.91 Mb
PubMed search [3] [4]
Wikidata
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Proline dehydrogenase, mitochondrial is an enzyme that in humans is encoded by the PRODH gene. [5] [6] [7]

Contents

The protein encoded by this gene is a mitochondrial proline dehydrogenase which catalyzes the first step in proline catabolism. Deletion of this gene has been associated with type I hyperprolinemia. The gene is located on chromosome 22q11.21, a region which has also been associated with the contiguous gene deletion syndromes: DiGeorge syndrome and CATCH22 syndrome. [7]

Function

Proline oxidase, or proline dehydrogenase, functions as the initiator of the proline cycle. Proline metabolism is especially important in nutrient stress because proline is readily available from the breakdown of extracellular matrix (ECM), and the degradation of proline through the proline cycle initiated by proline oxidase (PRODH), a mitochondrial inner membrane enzyme, can generate ATP. This degradative pathway generates glutamate and alpha-ketoglutarate, products that can play an anaplerotic role for the TCA cycle. The proline cycle is also in a metabolic interlock with the pentose phosphate pathway providing another bioenergetic mechanism. The induction of stress either by glucose withdrawal or by treatment with rapamycin, stimulated degradation of proline and increased PRODH catalytic activity. Under these conditions PRODH was responsible, at least in part, for maintenance of ATP levels. Activation of AMP-activated protein kinase (AMPK), the cellular energy sensor, by 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), also markedly upregulated PRODH and increased PRODH-dependent ATP levels, further supporting its role during stress. Glucose deprivation increased intracellular proline levels, and expression of PRODH activated the pentose phosphate pathway. Therefore, the induction of the proline cycle under conditions of nutrient stress may be a mechanism by which cells switch to a catabolic mode for maintaining cellular energy levels. [8]

Clinical significance

Mutations in the PRODH gene are associated with Proline Dehydrogenase deficiency. Many case studies have reported on this genetic disorder. In one such case study, 4 unrelated patients with HPI and a severe neurologic phenotype were shown to have the following common features: psychomotor delay from birth, often associated with hypotonia, severe language delay, autistic features, behavioral problems, and seizures. One patient who was heterozygous for a 22q11 microdeletion also had dysmorphic features. Four previously reported patients with HPI and neurologic involvement had a similar phenotype. This case study showed that Hyperprolinemia, Type I (HPI) may not always be a benign condition, and that the severity of the clinical phenotype appears to correlate with the serum proline level. [9] Still, in another case study, clinical features from 4 unrelated patients included early motor and cognitive developmental delay, speech delay, autistic features, hyperactivity, stereotypic behaviors, and seizures. All patients had increased plasma and urine proline levels. All patients had biallelic mutations in the PRODH gene, often with several variants on the same allele. Residual enzyme activity ranged from null in the most severely affected patient to 25 to 30% in those with a relatively milder phenotype. [10]

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References

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  2. 1 2 3 GRCm38: Ensembl release 89: ENSMUSG00000003526 - Ensembl, May 2017
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  4. "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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  7. 1 2 "Entrez Gene: PRODH proline dehydrogenase (oxidase) 1".
  8. Pandhare J, Donald SP, Cooper SK, Phang JM (Jul 2009). "Regulation and function of proline oxidase under nutrient stress". Journal of Cellular Biochemistry. 107 (4): 759–68. doi:10.1002/jcb.22174. PMC   2801574 . PMID   19415679.
  9. Afenjar A, Moutard ML, Doummar D, Guët A, Rabier D, Vermersch AI, Mignot C, Burglen L, Heron D, Thioulouse E, de Villemeur TB, Campion D, Rodriguez D (Oct 2007). "Early neurological phenotype in 4 children with biallelic PRODH mutations". Brain & Development. 29 (9): 547–52. doi:10.1016/j.braindev.2007.01.008. PMID   17412540. S2CID   43512139.
  10. Perry TL, Hardwick DF, Lowry RB, Hansen S (May 1968). "Hyperprolinaemia in two successive generations of a North American Indian family". Annals of Human Genetics. 31 (4): 401–7. doi:10.1111/j.1469-1809.1968.tb00573.x. PMID   4299764. S2CID   29894262.

Further reading