Single base deletion in exon 7 of the glycosylasparaginase gene causes a mild form of aspartylglycosaminuria in a patient of Mauritian origin

Aspartylglycosaminuria (AGU) is a lysosomal storage disorder of glycoprotein degradation caused by deficiency of glycosylasparaginase (GA). A deletion mutation was found in a mildly affected AGU patient whose parents are first-cousins of Mauritian origin. One bp deletion at position 787 or 788 (delta T788) in exon 7 of the GA gene resulted in a frameshift and produced an immediate stop codon. The resulting truncated polypeptide was defective in its post-translational proteolytic processing and remained as a single chain (36 kDa) with no GA activity.