Melittin is the main component of bee venom and the main pain-causing substance that can cause allergic reactions. When injected into animals and humans Melittin causes nociception and activates pain receptor cells through a variety of mechanisms. It also has a strong surface effect on cell membranes, leading to the formation of holes in epithelial cells and the destruction of red blood cells. As a result, bee stings can cause localized pain, swelling and redness of the skin, and in severe cases, life-threatening swelling of the throat and respiratory tract may occur. On the other hand, Bee venom therapy is also used in traditional medicine to treat various diseases. For example, it can act as a host defense peptide and exhibits powerful anti-tumor effects due to its cytolysis activity.

Melittin free acid is a honeybee venom polypeptide with antifungal activity.

From: Lee G, Bae H. Molecules. 2016;21(5):616.

Melittin free acid is a basic 26-amino-acid polypeptide, the major active ingredient of honeybee venom. Besides, Melittin free acid is an activator of phospholipase A2 (PLA2), an enzyme commonly found in mammalian tissues as well as in spider, insect and snake venom. The release of Melittin free acid from the bite leads to an increase in PLA2 activity, resulting in the release of arachidonic acid from the phospholipid membrane, leading to inflammation and pain at the site. It also has broad-spectrum antifungal activity against Fusarium culmorum, Candida albicans, Trichophyton rubrum et al. with MIC values of 0.4-60 μM. Melittin free acid hinders fungal growth by inducing cell apoptosis, repressing (1,3)-β-D-glucan synthase and participating in other pathways.

In some in vitro studies, Melittin free acid stimulates the biosynthesis of prostaglandin by mouse-transformed fibroblasts (MC5-5), human fibroblasts (D550), rabbit aorta endothelial cells , rat lung type II alveolar pneumocytes and rabbit smooth muscle cells. Moreover, Melittin free acid can stimulate the release of arachidonic acid from the cellular phospholipids of MC5-5 cells. And it can induce the accumulation of ROS in germinating conidia of A. flavus. In addition, Melittin free acid inhibits B. cinerea; MUCL 30158 and CECT 2100 strains with IC₅₀ values of 3.1 and 24 μM, respectively. In in vivo studies, Melittin can increase the levels of 13,14-dihydro-15-keto-PGE2 in the peripheral blood of mice by intraperitoneal inoculation.

In conclusion, Melittin free acid is a honeybee venom polypeptide with broad-spectrum antimicrobial activity.

References:

[1] A Hassid, et al. Res Commun Chem Pathol Pharmacol. 1977 Nov;18(3):507-17.

[2] Hamed Memariani, et al. Appl Microbiol Biotechnol. 2020 Aug;104(15):6513-6526.