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Hyperprolinemia type II results in proline levels in the blood between 10 and 15 times higher than normal, and high levels of a related compound called pyrroline-5-carboxylate. This rare form of the disorder may appear benign at times, [ 2 ] but often involves seizures, convulsions, and intellectual disability.
Other hydroxyprolines also exist in nature. The most notable ones are 2,3-cis-, 3,4-trans-, and 3,4-dihydroxyproline, which occurs in diatom cell walls [12] and are postulated to have a role in silica deposition. Hydroxyproline is also found in the walls of oomycetes, fungus-like protists related to diatoms.
Hence, this enzyme has one substrate, trans-4-hydroxy-L-proline, and one product, cis-4-hydroxy-D-proline. This enzyme belongs to the family of isomerases, specifically those racemases and epimerases acting on amino acids and derivatives. The systematic name of this enzyme class is 4-hydroxyproline 2-epimerase.
It is produced by Streptomyces mobaraensis fermentation in commercial quantities or extracted from animal blood, [13] and is used in a variety of processes, including the production of processed meat and fish products. Transglutaminase can be used as a binding agent to improve the texture of protein-rich foods such as surimi or ham. [14]
Hypoxia-inducible factor-proline dioxygenase contains iron, and requires ascorbate. Hypoxia-inducible factor (HIF) is an evolutionarily conserved transcription factor [ 7 ] that allows the cell to respond physiologically to low concentrations of oxygen. [ 8 ]
Ramaswamy SG (1983). "Conversion of 3-hydroxyproline to proline in the rat requires reduced pyridine-nucleotides". Fed. Proc. 42: 2232. Visser WF, Verhoeven-Duif NM, de Koning TJ (June 2012). "Identification of a human trans-3-hydroxy-L-proline dehydratase, the first characterized member of a novel family of proline racemase-like enzymes".
This enzyme is also called hydroxy-L-proline oxidase. This enzyme was originally thought to participate in the metabolism of arginine and proline . However, recent data show that it is unlikely since neither 4-oxo-L-proline nor cis -4-hydroxy-L-proline are metabolites of these metabolic pathways.
Proline dehydrogenase is in humans encoded by PRODH [1] and PRODH2 [2] genes, located on the chromosomes 22 and 19, respectively. Their mutations lead to hyperprolinemia, manifested by increased proline levels in blood and urine. The deficiency of PRODH has also been linked to the susceptibility to schizophrenia-4. [citation needed]