Dihydropyrimidinase deficiency: Phenotype, genotype and structural consequences in 17 patients.
Dihydropyrimidinase (DHP) is the second enzyme of the pyrimidine degradation pathway and catalyses the ring opening of 5,6-dihydrouracil and 5,6-dihydrothymine. To date, only 11 individuals have been reported suffering from a complete DHP deficiency. Here, we report on the clinical, biochemical and molecular findings of 17 newly identified DHP deficient patients as well as the analysis of the mutations in a three-dimensional framework. Patients presented mainly with neurological and gastrointestinal abnormalities and markedly elevated levels of 5,6-dihydrouracil and 5,6-dihydrothymine in plasma, cerebrospinal fluid and urine. Analysis of DPYS, encoding DHP, showed nine missense mutations, two nonsense mutations, two deletions and one splice-site mutation. Seventy-one percent of the mutations were located at exons 5-8, representing 41% of the coding sequence. Heterologous expression of 11 mutant enzymes in Escherichia coli showed that all but two missense mutations yielded mutant DHP proteins without significant activity. Only DHP enzymes containing the mutations p.R302Q and p.T343A possessed a residual activity of 3.9% and 49%, respectively. The crystal structure of human DHP indicated that the point mutations p.R490C, p.R302Q and p.V364M affect the oligomerization of the enzyme. In contrast, p.M70T, p.D81G, p.L337P and p.T343A affect regions near the di-zinc centre and the substrate binding site. The p.S379R and p.L7V mutations were likely to cause structural destabilization and protein misfolding. Four mutations were identified in multiple unrelated DHP patients, indicating that DHP deficiency may be more common than anticipated.
van Kuilenburg
André B P
AB
Laboratory Genetic Metabolic Diseases, Department of Clinical Chemistry, Academic Medical Center, Emma Children's Hospital, 1105 AZ Amsterdam, the Netherlands. a.b.vanKuilenburg@amc.uva.nl
Dobritzsch
Doreen
D
Meijer
Judith
J
Meinsma
Rutger
R
Benoist
Jean-François
JF
Assmann
Birgit
B
Schubert
Susanne
S
Hoffmann
Georg F
GF
Duran
Marinus
M
de Vries
Maaike C
MC
Kurlemann
Gerd
G
Eyskens
François J M
FJ
Greed
Lawrence
L
Sass
Jörn Oliver
JO
Schwab
K Otfried
KO
Sewell
Adrian C
AC
Walter
John
J
Hahn
Andreas
A
Zoetekouw
Lida
L
Ribes
Antonia
A
Lind
Suzanne
S
Hennekam
Raoul C M
RC
D000293:Adolescent; D000328:Adult; D000581:Amidohydrolases / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008659:Metabolic Diseases / Q000201:enzymology / Q000235:genetics*; D008954:Models, Biological; D008958:Models, Molecular; D010641:Phenotype; D055550:Protein Stability; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship; D055815:Young Adult
D000581:Amidohydrolases; C020047:dihydropyrimidinase