title: Identification of a human trans-3-hydroxy-L-proline dehydratase, the first characterized member of a novel family of proline racemase-like enzymes.
abstract: A family of eukaryotic proline racemase-like genes has recently been identified. Several members of this family have been well characterized and are known to catalyze the racemization of free proline or trans-4-hydroxyproline. However, the majority of eukaryotic proline racemase-like proteins, including a human protein called C14orf149, lack a specific cysteine residue that is known to be critical for racemase activity. Instead, these proteins invariably contain a threonine residue at this position. The function of these enzymes has remained unresolved until now. In this study, we demonstrate that three enzymes of this type, including human C14orf149, catalyze the dehydration of trans-3-hydroxy-L-proline to Δ(1)-pyrroline-2-carboxylate (Pyr2C). These are the first enzymes of this subclass of proline racemase-like genes for which the enzymatic activity has been resolved. C14orf149 is also the first human enzyme that acts on trans-3-hydroxy-L-proline. Interestingly, a mutant enzyme in which the threonine in the active site is mutated back into cysteine regained 3-hydroxyproline epimerase activity. This result suggests that the enzymatic activity of these enzymes is dictated by a single residue. Presumably, human C14orf149 serves to degrade trans-3-hydroxy-L-proline from the diet and originating from the degradation of proteins that contain this amino acid, such as collagen IV, which is an important structural component of basement membrane.
authors.affiliation: Department of Metabolic Diseases, University Medical Center Utrecht/Wilhelmina Children's Hospital Utrecht, 3508 AB Utrecht, The Netherlands. w.visser-2@umcutrecht.nl
authors.forename: Wouter F
authors.initials: WF
authors.lastname: Visser
authors.forename: Nanda M
authors.initials: NM
authors.lastname: Verhoeven-Duif
authors.forename: Tom J
authors.initials: TJ
authors.lastname: de Koning
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry* / Q000235:genetics*; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D019757:Carbon-Oxygen Lyases / Q000737:chemistry* / Q000235:genetics*; D002384:Catalysis; D020134:Catalytic Domain; D003001:Cloning, Molecular; D003545:Cysteine / Q000737:chemistry; D015971:Gene Expression Regulation, Enzymologic; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D006909:Hydroxyproline / Q000737:chemistry; D008954:Models, Biological; D009154:Mutation; D016366:Open Reading Frames; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D014018:Tissue Distribution
chemical_list: D005982:Glutathione Transferase; D019757:Carbon-Oxygen Lyases; C575022:L3HYPDH protein, human; D000591:Amino Acid Isomerases; C022451:proline racemase; D003545:Cysteine; D006909:Hydroxyproline