Antimicrobial peptide with potent activity against Gram-negative bacteria (PubMed:24704757). Shows immunostimulatory actions both in vitro and in vivo (PubMed:24704757, PubMed:25861850, PubMed:28526557). In vitro, is cytotoxic to non-small cell lung adenocarcinoma A549 cells (PubMed:24704757). Also, stimulates production of pro-inflammatory cytokines by mouse peritoneal macrophages and down-regulates production of the anti-inflammatory cytokine IL-10 by lipopolysaccharide (LPS)-stimulated cells (PubMed:24704757). In vivo, intraperitoneal injection in mice enhances the activation state and homing capacity of Th1 type lymphocytes and promotes the recruitment, activation and tumoricidal capacities of peritoneal NK cells (PubMed:25861850, PubMed:28526557). Has a very weak activity in stimulation of insulin release and a weak hemolytic activity (PubMed:27049440, PubMed:30244134). Antimicrobial peptide with potent activity against some Gram-positive and Gram-negative bacteria (PubMed:30044391). Has a multifunctional mode of action (PubMed:30044391). It displays depolarization and bacterial cell leakage, and can also internalize into bacterial cells and alter specific gene expression involved in bacterial resistance mechanisms (PubMed:30044391). Does not agglutinate bacteria and lipid vesicles, even a high concentrations (PubMed:30044391). Also displays moderate cellular protection against yellow fever virus (YFV)-infected Vero cells without causing significant cytotoxicity (PubMed:27049440). Shows a weak hemolytic activity, and is not cytotoxic to monocytes (PubMed:30044391). Frenatin 2.3S (version without Gly-71) shows no or very weak antibacterial activity, shows no or very weak cytotoxicity to lung adenocarcinoma A549 cells and shows very weak hemolysis (PubMed:24704757). It only stimulates production of pro-inflammatory cytokines IL-23 (but not IL-1beta and TNF-alpha) by mouse peritoneal macrophages and has no effect on the production of the anti-inflammatory cytokine IL-10 (PubMed:24704757). Frenatin 2.3S (version without Gly-71) very weakly stimulates insulin release (PubMed:30244134). Expressed by the skin glands. Frenatin 2.3S is not amidated. Frenatin 2.1S, amidated. Frenatin 2.3S, without Gly-71, non-amidated. May be regarded as a candidate for antitumor immunotherapy, since an injection of this peptide led to a marked increase in the number and tumoricidal capacity of activated peritoneal natural killer (NK) cells in the peritoneal cavity. Belongs to the frog skin active peptide (FSAP) family. Frenatin subfamily. A paper describes Frenatin 2.3S as a non-amidated peptide of 17 amino acids (PubMed:27049440). In contrast, another report describes it as a non-amidated peptide of 16 amino acids (PubMed:24704757). Since the absence of a C-terminal Gly is generally explained by the activity of Gly as an amide donor, it is possible that Frenatin 2.3S described by PubMed:24704757 comes from another gene, and should be presented in another entry.