Conformational studies on the N-linked carbohydrate chain of bromelain

Abstract

1H- and 13C-NMR assignments for the carbohydrate part of the glycopeptide alpha-d-Man-(1->6)-[ß-d-Xyl-(1->2)]-ß-d-Man-(1->4)-ß-d-GlcNAc-(1->4)-[alpha-l-Fuc-(1->3)]-ß-d- GlcNAc-(1->N)-Asn~, derived from the proteolytic enzyme bromelain (EC 3.4.22.4), have been obtained using homo- and heteronuclear correlation spectroscopy, two-dimensional homonuclear Hartmann-Hahn and nuclear Overhauser enhancement experiments. A conformational model for the carbohydrate chain, deduced from the NMR data and consistent with hard-sphere exo-anomeric calculations shows that the rotamer population about the C-5C-6 bond of ß-Man is restricted to the omega=180 rotamer, mainly.