MISSENSE MUTATIONS IN THE HUMAN GLUTATHIONE SYNTHETASE GENE RESULT INSEVERE METABOLIC-ACIDOSIS, 5-OXOPROLINURIA, HEMOLYTIC-ANEMIA AND NEUROLOGICAL DYSFUNCTION

Severe glutathione synthetase (GS) deficiency is a rare genetic disord er with neonatal onset, The enzymatic block of the gamma-glutamyl cycl e leads to a generalized glutathione deficiency, Clinically affected p atients present with severe metabolic acidosis, 5-oxoprolinuria, incre ased rate of hemolysis and defective function of the central nervous s ystem, The disorder is inherited in an recessive mode and, until recen tly, the basis has remained unknown, We have 18 GS alleles associated with enzyme deficiency and we detected missense mutations by direct se quencing of cDNAs and genomic DNA, In total, 13 different mutations we re identified, Four patients were found to be compound heterozygotes a nd two individuals were apparently homozygous, Reduced enzymatic activ ities were demonstrated in recombinant protein expressed from cDNAs in four cases with different missense mutations, The results from bioche mical analysis of patient specimens, supported by the properties of th e expressed mutant proteins, indicate that a residual activity is pres ent in affected individuals, Our results suggest that complete loss of function of both GS alleles is probably lethal, It is postulated that missense mutations will account for the phenotype in the majority of patients with severe GS deficiency.