Antimicrobial peptide that has a large activity spectrum with activity against Gram-positive, Gram-negative bacteria, as well as against fungi. Shows activity at micromolar concentrations. Displays minimal inhibitory concentration (MIC) values lower than minimal bactericidal concentrations (MBC). May have a dual mode of action depending on the peptide concentrations. At MIC concentrations, the peptide penetrates into the cytoplasm of target cells (tested on the Gram-negative E.Coli). The two inner membrane proteins YgdD and SbmA may be required for this uptake. At concentrations higher than MIC, arasin may act by disrupting membranes. Does not show hemolytic activity. Interacts with chitin through the N-terminal region (26-48). This interaction may be important, since chitin is a component of the fungal cell wall, as well as of the crab exoskeleton (permitting a possible action of arasin in wound healing in case of lesions). Mainly expressed in hemocytes. No or very low expression in heart, gills, inestines, and epidermis. Disulfide bonds are important for activity especially against Gram-negative bacteria, since the linearization of the peptide causes a strong decrease of activity on these bacteria.