Isolation and biochemical characterization of mucus proteins in Japanese bunching onion (allium fistulosum) green leaves

Proteins contained in the green leaf mucus of Japanese bunching onion (Allium fistulosum L.) were isolated by ammonium sulfate precipitation and separated by hydrophobic interaction chromatography. The mucus proteins had an enhanced effect on tumor necrosis factor (TNF)-á production in the RAW 264 murine macrophage cell line. Protein composition was analyzed by SDS-polyacrylamide gel electrophoresis and N-terminal amino acid sequencing. The effect on RAW 264 cells was mainly attributed to mannose-binding lectin and thaumatin-like proteins, which occupied 34% of the mucus proteins. Other major proteins contained in the mucus showed homologous amino acid sequences to those of lachrymatory factor synthase, β-1,3-glucanase, 2S albumin precursor, and pathogenesis-related protein 4. Protein composition ratios in the mucus of 13 cultivars of Japanese bunching onion were also examined. Taken together, the green leaf mucus of Japanese bunching onion may be a possible source of various bioactive proteins.