Defensins

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Introduction

The defensin was first named by Robert Lehrer of the United States in 1980. It is a small molecule short peptide that can antagonize microorganisms and some malignant cells produced by the organism in the defense against pathogens. Defensins usually consist of 29 to 54 amino acids, including 6 to 8 conserved cysteines, which form an antiparallel β-sheet or alpha-helical structure through a cysteine intramolecular disulfide bond. Defensin is structurally stable and has a very broad spectrum of antibacterial activity. It can be divided into animal defensins, plant defensins and insect defensins depending on the source. Defensin has a stable molecular structure and a broad spectrum of antibacterial activity. According to different molecular structural characteristics, animal defensins can be divided into three types: α-defensin, β-defensin, and θ-defensin.

Mechanism of action

The antibacterial mechanism of defensin has two different mechanisms of antibacterial action, one is the independent membrane mechanism, and the other is the mechanism by which defensin binds to intracellular complexes. The independent membrane mechanism holds that positively charged defensins and negatively charged bacterial cell membranes attract each other and bind to each other, thereby destroying the integrity of the phospholipid bilayer and causing fissures in the target cell membrane.

Application of defensins

Studies have found that defensins in intestinal epithelial cells play a natural barrier to the intestinal mucosa, and the decrease in the expression level of defensins leads to adhesion of mucosal bacteria and invasion of the body to trigger an inflammatory response. Chronic inflammatory diseases of the intestine, Crohn' disease (CD) and ulcerative colitis (UC), are associated with abnormal expression of the ileal Pandemic cell defenses HD-5 and HD-6. Defensins have a relationship with chronic obstructive pulmonary disease. Defensin HBD-2 is closely related to respiratory diseases and plays an important role in lung mucosal defense. PMX-30063 is an antibiotic drug that mimics defensins and has a completely new mechanism of action, and bacteria are less susceptible to resistance. It is active against both Gram-positive and Gram-negative bacteria, it kills cells directly and sterilizes faster than many antibiotics.

References

1. Kovalzon, V. M. , & Strekalova, T. V. . (2006). Delta sleep-inducing peptide (dsip): a still unresolved riddle . Journal of Neurochemistry, 97(2), 7.
2. Bobyntsev, I. I. , Kryukov, A. A. , Belykh, A. E. , & Dudka, V. T. . (2016). Effect of delta sleep-inducing peptide on functional state of hepatocytes in rats during restraint stress. Bulletin of Experimental Biology and Medicine, 160(4), 421-424.