new sugar chain of the proteinase inhibitor from latex of Carica papaya

The structure of a sugar chain of the proteinase inhibitor from the latex of Carica papaya was studied. Sugar chains liberated on hydrazinolysis were N-acetylated, and their reducing-end residues were tagged with 2-aminopyridine. One major sugar chain was detected on size-fractionation and reversed-phase HPLC analyses. The structure of the PA-sugar chain was determined by two-dimensional sugar mapping combined with sequential exoglycosidase digestion and partial acid hydrolysis, and by 750 MHz 1H-NMR spectroscopy. The structure found was Manα1–6(Manα1–3)Manα1–6(Manα1–3)(Xylβ1–2) Manβ1–4GlcNAcβ1–4(Fucα1–3)GlcNAc. This sugar chain represents a new plant-type sugar chain with five mannose residues.