Identification of 4-N-2-acetamido-2-deoxy-beta-D-glucopyranosyl-L-asparagine in biological materials by gas chromatography-mass spectrometry.

A specific and sensitive method for the identification of 4-N-2-acetamido-2-deoxy-beta-D-glucopyranosyl-L-asparagine (GlcNAc-Asn) in urine in aspartylglycosaminuria and in hydrolysates of glycoproteins is described. The method involves permethylation of GlcNAc-Asn followed by gas chromatographic-mass spectrometric analysis of the methylated derivative. It can be used to confirm the diagnosis of aspartylglycosaminuria and to assess the excretion of GlcNAc-Asn in urine during various phases of the disease. The presence of an N-acetylglucosaminyl-asparagine type of carbohydrate-peptide linkage in a glycoprotein can be determined by applying the method to the partial acid hydrolysate of a proteolytically digested glycoprotein.