Nonketotic hyperglycinemia (NKH) is an autosomal recessive metabolic disorder caused by the defects in the glycine cleavage system (GCS; EC 2.1.2.10), a multienzyme system that consists of four individual components.
Structural and expression analyses of normal and mutant mRNA encoding glycine decarboxylase: three-base deletion in mRNA causes nonketotic hyperglycinemia.
In this study, we describe the screening of the entire GLDC gene in 3 NKH families by D-HPLC analysis of all 25 exons, identifying two point mutations and two large deletions (exon 8 and exons 2-15) using a combination of D-HPLC analysis, long range PCR, Southern blot and sequencing.
The in vitro expression analysis of the identified GLDC mutations revealed considerable residual enzyme activity, suggesting prognostic and enzymatic heterogeneity even in neonatal-onset nonketotic hyperglycinemia.
The 4 to 6% of normally spliced GLDC mRNA in the patients may account for their relatively favorable clinical outcome compared with patients with classic glycine encephalopathy.
Three of four nonketotic hyperglycinemia patients homozygous for a novel GLDC mutation (A802V) were treated by assisted respiration and/or sodium benzoate with or without ketamine and had transient neonatal or absent symptoms and normal developmental outcome, despite persisting biochemical evidence of nonketotic hyperglycinemia.
Human glycine decarboxylase gene (GLDC) and its highly conserved processed pseudogene (psiGLDC): their structure and expression, and the identification of a large deletion in a family with nonketotic hyperglycinemia.