1. β-Ureidopropionase deficiency due to novel and rare UPB1 mutations affecting pre-mRNA splicing and protein structural integrity and catalytic activity
- Author
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Doreen Dobritzsch, Judith Meijer, Rutger Meinsma, Dirk Maurer, Ardeshir A. Monavari, Anders Gummesson, Annika Reims, Jorge A. Cayuela, Natalia Kuklina, Jean-François Benoist, Laurence Perrin, Birgit Assmann, Georg F. Hoffmann, Jörgen Bierau, Angela M. Kaindl, André B.P. van Kuilenburg, Laboratory Genetic Metabolic Diseases, AGEM - Amsterdam Gastroenterology Endocrinology Metabolism, Clinical Genetics, MUMC+: DA KG Lab Centraal Lab (9), and RS: FHML non-thematic output
- Subjects
Purine-Pyrimidine Metabolism, Inborn Errors ,Endocrinology, Diabetes and Metabolism ,beta-Ureidopropionase ,Minigene approach ,Biochemistry ,AMINOISOBUTYRIC ACID ,Amidohydrolases ,MECHANISMS ,Neurological abnormalities ,Endocrinology ,SDG 3 - Good Health and Well-being ,GENETIC-ANALYSIS ,Genetics ,RNA Precursors ,Animals ,Humans ,Abnormalities, Multiple ,CRYSTAL-STRUCTURE ,WHITE FAT ,HOMOCARNOSINE ,Molecular Biology ,Medicinsk genetik ,Functional and structural protein analysis ,Mammals ,Brain Diseases ,Movement Disorders ,PURIFICATION ,Crystal structure ,UPB1 ,DIHYDROPYRIMIDINE DEHYDROGENASE ,ALANINE SYNTHASE ,Mutation ,beta-Alanine ,CARNOSINE ,Medical Genetics ,ß-Ureidopropionase - Abstract
beta-Ureidopropionase is the third enzyme of the pyrimidine degradation pathway and catalyses the conversion of N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyric acid to beta-alanine and beta-aminoisobutyric acid, ammonia and CO2. To date, only a limited number of genetically confirmed patients with a complete beta-ureidopropionase deficiency have been reported. Here, we report on the clinical, biochemical and molecular findings of 10 newly identified beta-ureidopropionase deficient individuals. Patients presented mainly with neurological abnormalities and markedly elevated levels of N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyric acid in urine. Analysis of UPB1, encoding beta-ureidopropionase, showed 5 novel missense variants and two novel splice-site variants. Functional expression of the UPB1 variants in mammalian cells showed that recombinant beta-ureidopropionase carrying the p.Ala120Ser, p.Thr129Met, p.Ser300Leu and p.Asn345Ile variant yielded no or significantly decreased beta-ureidopropionase activity. Analysis of the crystal structure of human beta-ureidopropionase indicated that the point mutations affect substrate binding or prevent the proper subunit association to larger oligomers and thus a fully functional beta-ureidopropionase. A minigene approach showed that the intronic variants c.[364 + 6 T > G] and c.[916 + 1_916 + 2dup] led to skipping of exon 3 and 8, respectively, in the process of UPB1 pre-mRNA splicing. The c.[899C > T] (p.Ser300Leu) variant was identified in two unrelated Swedish beta-ureidopropionase patients, indicating that beta-ureidopropionase deficiency may be more common than anticipated.
- Published
- 2022