Structural characterization and insights into the formation of N-acetylglucosaminylasparagine and its derivatives in NGLY1-deficient models and patients

This study examined the Asn-GlcNAc biosynthetic pathway, demonstrating that cytosolic endo-β-N-acetylglucosaminidase (ENGase), the proteasome, and peptidases are essential for its generation. NGLY1-deficient models and patients exhibited accumulation of novel elongated forms of Asn-GlcNAc, including Asn-GlcNAc-GalNAc, Asn-GlcNAc-Gal, and Asn-GlcNAc-Gal-NeuAc, in cells, culture supernatant, plasma, and urine. Our findings indicate that Asn-GlcNAc and Asn-oligosaccharides (Asn-OSs) may serve as promising diagnostic tools for NGLY1 deficiency.