Novel mutations in 3-phosphoglycerate dehydrogenase (PHGDH) are distributed throughout the protein and result in altered enzyme kinetics
- 20 February 2009
- journal article
- research article
- Published by Hindawi Limited in Human Mutation
- Vol. 30 (5), 749-756
- https://doi.org/10.1002/humu.20934
Abstract
Three-phosphoglycerate dehydrogenase (3-PGDH) deficiency is a rare recessive inborn error in the biosynthesis of the amino acid L-serine characterized clinically by congenital microcephaly, psychomotor retardation, and intractable seizures. The biochemical abnormalities associated with this disorder are low concentrations of L-serine, D-serine, and glycine in cerebrospinal fluid (CSF). Only two missense mutations (p.V425M and p.V490M) have been identified in PHGDH, the gene encoding 3-PGDH, but it is currently unclear how these mutations in the carboxy-terminal regulatory domain of the protein affect enzyme function. We now describe five novel mutations in five patients with 3-PGDH deficiency; one frameshift mutation (p.G238fsX), and four missense mutations (p.R135W, p.V261M, p.A373T, and p.G377S). The missense mutations were located in the nucleotide binding and regulatory domains of 3-PGDH and did not affect steady-state expression, protein stability, and protein degradation rates. Patients' fibroblasts displayed a significant, but incomplete, reduction in maximal enzyme activities associated with all missense mutations. In transient overexpression studies in HEK293T cells, the p.A373T, p.V425M, and p.V490M mutations resulted in almost undetectable enzyme activities. Molecular modeling of the p.R135W and p.V261M mutations onto the partial crystal structure of 3-PGDH predicted that these mutations affect substrate and cofactor binding. This prediction was confirmed by the results of kinetic measurements in fibroblasts and transiently transfected HEK293T cells, which revealed a markedly decreased Vmax and an increase in Km values, respectively. Taken together, these data suggest that missense mutations associated with 3-PGDH deficiency either primarily affect substrate binding or result in very low residual enzymatic activity. Hum Mutat 0, 1–8, 2009.This publication has 32 references indexed in Scilit:
- Phosphoserine Aminotransferase Deficiency: A Novel Disorder of the Serine Biosynthesis PathwayAmerican Journal of Human Genetics, 2007
- D‐serine in the developing human central nervous systemAnnals of Neurology, 2006
- Treatment with amino acids in serine deficiency disordersJournal of Inherited Metabolic Disease, 2005
- Mutations responsible for 3-phosphoserine phosphatase deficiencyEuropean Journal of Human Genetics, 2003
- Selective expression of L-serine synthetic enzyme 3PGDH in Schwann cells, perineuronal glia, and endoneurial fibroblasts along rat sciatic nerves and its upregulation after crush injury.Archives of Histology and Cytology, 2003
- V490M, a Common Mutation in 3-Phosphoglycerate Dehydrogenase Deficiency, Causes Enzyme Deficiency by Decreasing the Yield of Mature EnzymeOnline Journal of Public Health Informatics, 2002
- Phenotypic Heterogeneity and Adverse Effects of Serine Treatment in 3-Phosphoglycerate Dehydrogenase Deficiency: Report on Two SiblingsNeuropediatrics, 2001
- Hypomyelination and Reversible White Matter Attenuation in 3-Phosphoglycerate Dehydrogenase DeficiencyNeuropediatrics, 2000
- The Contribution of Adjacent Subunits to the Active Sites ofd-3-Phosphoglycerate DehydrogenaseOnline Journal of Public Health Informatics, 1999
- Kinetics of Neutral Amino Acid Transport Across the Blood‐Brain BarrierJournal of Neurochemistry, 1987