gamma-Glutamylglutamine identified in plasma and cerebrospinal fluid from hyperammonaemic patients.

gamma-Glutamylglutamine has been identified in plasma and cerebrospinal fluid. Preparative high voltage electrophoresis was used to isolate the compound from two to three ml of sample. Analysis of archival material from eight patients with urea cycle disorders showed that plasma gamma-glutamylglutamine was 20-214 mumol/l when the plasma glutamine was greater than 1,000 mumol/l and that the relationship was strongly positive (P less than 0.0005). Plasma gamma-glutamylglutamine concentration was also raised in one patient with secondary hyperammonaemia, but not in three other cases, one of whom had a plasma glutamine of 10,000 mumol/l. Cerebrospinal fluid from the last patient contained 97 mumol/l of gamma-glutamylglutamine. Samples of cerebrospinal fluid from two patients with urea cycle disorders were available and the gamma-glutamylglutamine levels were 203 and 313 mumol/l. gamma-Glutamylglutamine and 5-oxoproline concentrations were not significantly increased in urine from any of these patients.