title: Recurrence of carbamoyl phosphate synthetase 1 (CPS1) deficiency in Turkish patients: characterization of a founder mutation by use of recombinant CPS1 from insect cells expression.
abstract: Carbamoyl phosphate synthetase 1 (CPS1) deficiency due to CPS1 mutations is a rare autosomal-recessive urea cycle disorder causing hyperammonemia that can lead to death or severe neurological impairment. CPS1 catalyzes carbamoyl phosphate formation from ammonia, bicarbonate and two molecules of ATP, and requires the allosteric activator N-acetyl-L-glutamate. Clinical mutations occur in the entire CPS1 coding region, but mainly in single families, with little recurrence. We characterized here the only currently known recurrent CPS1 mutation, p.Val1013del, found in eleven unrelated patients of Turkish descent using recombinant His-tagged wild type or mutant CPS1 expressed in baculovirus/insect cell system. The global CPS1 reaction and the ATPase and ATP synthesis partial reactions that reflect, respectively, the bicarbonate and the carbamate phosphorylation steps, were assayed. We found that CPS1 wild type and V1013del mutant showed comparable expression levels and purity but the mutant CPS1 exhibited no significant residual activities. In the CPS1 structural model, V1013 belongs to a highly hydrophobic β-strand at the middle of the central β-sheet of the A subdomain of the carbamate phosphorylation domain and is close to the predicted carbamate tunnel that links both phosphorylation sites. Haplotype studies suggested that p.Val1013del is a founder mutation. In conclusion, the mutation p.V1013del inactivates CPS1 but does not render the enzyme grossly unstable or insoluble. Recurrence of this particular mutation in Turkish patients is likely due to a founder effect, which is consistent with the frequent consanguinity observed in the affected population.
authors.affiliation: Division of Metabolism, University Children's Hospital, 8032 Zurich, Switzerland; Children's Research Center, 8032 Zurich, Switzerland; Neuroscience Center Zurich, University and ETH Zurich, Switzerland.
authors.forename: Liyan
authors.initials: L
authors.lastname: Hu
authors.affiliation: Division of Metabolism, University Children's Hospital, 8032 Zurich, Switzerland; Children's Research Center, 8032 Zurich, Switzerland; Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Diez-Fernandez
authors.affiliation: Division of Metabolism, University Children's Hospital, 8032 Zurich, Switzerland; Children's Research Center, 8032 Zurich, Switzerland.
authors.forename: Véronique
authors.initials: V
authors.lastname: Rüfenacht
authors.affiliation: Department of Pediatric Metabolic Diseases, Ihsan Dogramaci Children's Hospital, Hacettepe University, Ankara, Turkey; Gaziantep Children's Hospital, Gaziantep, Turkey.
authors.forename: Burcu Öztürk
authors.initials: BÖ
authors.lastname: Hismi
authors.affiliation: Department of Pediatric Metabolic Diseases, Ihsan Dogramaci Children's Hospital, Hacettepe University, Ankara, Turkey; Erzurum Regional Training and Research Hospital, Erzurum, Turkey.
authors.forename: Özlem
authors.initials: Ö
authors.lastname: Ünal
authors.affiliation: Department of Pediatric Metabolic Disease, Medical School, Akdeniz University, Antalya, Turkey.
authors.forename: Erdogan
authors.initials: E
authors.lastname: Soyucen
authors.affiliation: Department of Pediatric Metabolic Disease, Medical School, Ege University, Bornova, Izmir, Turkey.
authors.forename: Mahmut
authors.initials: M
authors.lastname: Çoker
authors.affiliation: Division of Neonatology, Department of Pediatrics, Bezmialem Vakif University, Istanbul, Turkey.
authors.forename: Bilge Tanyeri
authors.initials: BT
authors.lastname: Bayraktar
authors.affiliation: Ankara Cocuk Sagligi ve Hastaliklari, Cocuk Beslenme & Metabolizma Unitesi, Diskapi, Ankara, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Gunduz
authors.affiliation: Department of Pediatric Metabolic Diseases, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey.
authors.forename: Ertugrul
authors.initials: E
authors.lastname: Kiykim
authors.affiliation: Division of Metabolism and Nutrition, Gazi University Hospital, Ankara, Turkey.
authors.forename: Asburce
authors.initials: A
authors.lastname: Olgac
authors.affiliation: Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain; Centro de Investigación Biomédica en Red para Enfermedades Neurodegenerativas (CIBERNED-ISCIII), Valencia, Spain; Instituto de Investigación Sanitaria La Fe, Valencia, Spain.
authors.forename: Jordi
authors.initials: J
authors.lastname: Pérez-Tur
authors.affiliation: Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain; Group 739, Centro de Investigación Biomédica en Red para Enfermedades Raras (CIBERER-ISCIII), Valencia, Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Rubio
authors.affiliation: Division of Metabolism, University Children's Hospital, 8032 Zurich, Switzerland; Children's Research Center, 8032 Zurich, Switzerland; Neuroscience Center Zurich, University and ETH Zurich, Switzerland. Electronic address: Johannes.Haeberle@kispi.uzh.ch.
authors.forename: Johannes
authors.initials: J
authors.lastname: Häberle
mesh_terms: D000818:Animals; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020165:Carbamoyl-Phosphate Synthase I Deficiency Disease / Q000235:genetics*; D004795:Enzyme Stability; D005260:Female; D018703:Founder Effect; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins; D017384:Sequence Deletion; D061987:Sf9 Cells; D018411:Spodoptera; D014421:Turkey
chemical_list: D011993:Recombinant Fusion Proteins; D002222:Carbamoyl-Phosphate Synthase (Ammonia)
keywords: Baculovirus/insect cell expression system; Carbamoyl phosphate synthetase 1 (CPS1) deficiency; Enzyme activity; Founder mutation; Thermostability; Urea cycle disorder