Ascalin, a new anti-fungal peptide with human immunodeficiency virus type 1 reverse transcriptase-inhibiting activity from shallot bulbs.

An isolation procedure comprising ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-Sepharose and gel filtration on Superdex 75 was used to isolate an anti-fungal peptide from the bulbs of the shallot Allium ascalonicum. The peptide demonstrated a molecular weight of 9.5kDa, and possessed an N-terminal sequence YQCGQGG somewhat similar to chitinases from other Allium species which are however much larger in molecular weight. The peptide designated ascalin manifested a unique specific anti-fungal activity. It inhibited mycelial growth in the fungus Botrytis cinerea but not in the fungi Mycosphaerella arachidicola and Fusarium oxysporum. Ascalin inhibited HIV-1 reverse transcriptase with an IC(50) of 10 microM, much more potently than Allium tuberosum anti-fungal protein and other anti-fungal proteins.