1-Deoxyfuconojirimycin HCl (DFJ) is a potent inhibitor of α-L-fucosidase, a key glycosidase enzyme involved in the hydrolysis of fucose residues from glycoconjugates. It is primarily used in biochemical and glycobiology research to study carbohydrate metabolism, glycoprotein processing, and lysosomal degradation pathways.

By selectively inhibiting α-L-fucosidase, DFJ enables researchers to investigate the enzyme's role in biological processes such as cell adhesion, signaling, and pathogen interactions. It is particularly valuable in models of fucosidosis, a lysosomal storage disorder, and in exploring therapeutic interventions for such conditions.

In virology, DFJ has applications in studying viral replication and host cell interactions, as fucosylation is implicated in the infectivity of viruses like HIV and norovirus. This makes it a tool for developing antiviral strategies targeting glycan processing.

Overall, DFJ serves as an essential reagent in basic and applied research, advancing understanding of fucose-related glycobiology and potential treatments for associated diseases. It is not typically used for general glycosidase inhibition like α-glucosidase inhibitors in diabetes management.