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 Liyan Hu a,b,c , Carmen Diez-Fernandez a,b,d , Véronique Rüfenacht a,b , Burcu Öztürk Hismi e,f , Özlem Ünal e,g , Erdogan Soyucen h , Mahmut Çoker i , Bilge Tanyeri Bayraktar j , Mehmet Gunduz k , Ertugrul Kiykim l , Asburce Olgac m , Jordi Pérez-Tur d,n,o , Vicente Rubio d,p , Johannes Häberle a,b,c, ⁎ a Division of Metabolism, University Children's Hospital, 8032 Zurich, Switzerland b Children's Research Center, 8032 Zurich, Switzerland c Neuroscience Center Zurich, University and ETH Zurich, Switzerland d Instituto de Biomedicina de Valencia (IBV-CSIC), Valencia, Spain e Department of Pediatric Metabolic Diseases, Ihsan Dogramaci Children's Hospital, Hacettepe University, Ankara, Turkey f Gaziantep Children's Hospital, Gaziantep, Turkey g Erzurum Regional Training and Research Hospital, Erzurum, Turkey h Department of Pediatric Metabolic Disease, Medical School, Akdeniz University, Antalya, Turkey i Department of Pediatric Metabolic Disease, Medical School, Ege University, Bornova, Izmir, Turkey j Division of Neonatology, Department of Pediatrics, Bezmialem Vakif University, Istanbul, Turkey k Ankara Cocuk Sagligi ve Hastaliklari, Cocuk Beslenme & Metabolizma Unitesi, Diskapi, Ankara, Turkey l Department of Pediatric Metabolic Diseases, Cerrahpasa Medical Faculty, Istanbul University, Istanbul, Turkey m Division of Metabolism and Nutrition, Gazi University Hospital, Ankara, Turkey n Centro de Investigación Biomédica en Red para Enfermedades Neurodegenerativas (CIBERNED-ISCIII), Valencia, Spain o Instituto de Investigación Sanitaria La Fe, Valencia, Spain p Group 739, Centro de Investigación Biomédica en Red para Enfermedades Raras (CIBERER-ISCIII), Valencia, Spain abstract article info Article history: Received 9 September 2014 Received in revised form 30 September 2014 Accepted 30 September 2014 Available online xxxx Keywords: Urea cycle disorder Carbamoyl phosphate synthetase 1 (CPS1) deficiency Founder mutation Baculovirus/insect cell expression system Enzyme activity Thermostability 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 main- ly 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 carba- mate 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. © 2014 Elsevier Inc. All rights reserved. 1. Introduction Carbamoyl phosphate synthetase 1 deficiency (CPS1D; OMIM #237300) caused by mutations in the human Carbamoyl phosphate synthetase 1 (CPS1, MIM #608307) gene is a rare autosomal-recessive urea cycle disorder (UCD) with an estimated incidence of 1:50,000– 1:300,000 based on the reports of the Japanese and American cohorts Molecular Genetics and Metabolism xxx (2014) xxx–xxx Abbreviations: hCPS1, human carbamoyl phosphate synthetase 1; CPS1D, carbamoyl phosphate synthetase 1 deficiency; DSF, differential scanning fluorimetry; V1013del, CPS1-valine 1013 deletion; CP, carbamoyl phosphate; NAG, N-acetyl-L-glutamate. ⁎ Corresponding author at: University Children's Hospital Zurich, Division of Metabolism, 8032 Zurich, Switzerland. Fax: +41 44 266 7167. E-mail address: Johannes.Haeberle@kispi.uzh.ch (J. Häberle). YMGME-05816; No. of pages: 7; 4C: 5 http://dx.doi.org/10.1016/j.ymgme.2014.09.014 1096-7192/© 2014 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Molecular Genetics and Metabolism journal homepage: www.elsevier.com/locate/ymgme Please cite this article as: L. Hu, et al., Recurrence of carbamoyl phosphate synthetase 1 (CPS1) deficiency in Turkish patients: Characterization of a founder mutation by us..., Mol. Genet. Metab. (2014), http://dx.doi.org/10.1016/j.ymgme.2014.09.014