Antimicrobial peptides (AMPs) are short, cationic peptides found in various living organisms, including bacteria, plants, animals, and humans. They play a crucial role in the innate immune systems of these organisms by interacting with the cell membranes of pathogens such as viruses, bacteria, and fungi. AMPs can act against both Gram-positive and Gram-negative pathogens through various mechanisms, including membrane disruption, targeting intracellular organelles, and inhibiting nucleic acid and protein synthesis. This review focuses on AMPs from plants, animals, and humans, discussing their structures, modes of action, and potential applications. **Plants:** - **Structures:** Plant AMPs are typically cysteine-rich and form multiple disulfide bonds, giving them a compact structure. They include thionins, defensins, hevein-like peptides, knottins, α-hairpinins, lipid transfer proteins, snakins, and non-cysteine-rich peptides. - ** Modes of Action:** Plant AMPs can disrupt cell membranes, form pores, and interfere with intracellular processes. They have broad-spectrum activity against bacteria, fungi, and viruses. **Animals:** - **Structures:** Animal AMPs are categorized into defensins and cathelicidins. Defensins are cationic and composed of 29 to 42 amino acids with three pairs of disulfide bonds. Cathelicidins vary in size and structure but are positively charged and amphipathic. - ** Modes of Action:** Animal AMPs target both Gram-positive and Gram-negative bacteria. They can permeabilize cell membranes, inhibit protein synthesis, and disrupt intracellular pathways. **Humans:** - **Structures:** Human AMPs, primarily cathelicidins, include LL-37, cathelicidin 4 (indolocidin), protegrins, and histatins. They have antibacterial, antifungal, and antiviral activities. - ** Modes of Action:** Human AMPs can target viral envelopes, prevent viral binding to host cells, and interfere with viral replication. They also act on bacterial membranes and intracellular targets, such as nucleic acids and proteins. **Modes of Action and Mechanisms:** - **Antiviral AMPs:** Target viral envelopes, prevent viral binding to host cells, and interfere with viral replication. - **Antibacterial AMPs:** Interact with negatively charged bacterial membranes, causing membrane instability and disruption. - **Antifungal AMPs:** Similar to antibacterial AMPs, they target fungal cell walls and intracellular components. - **Membrane-Targeting AMPs:** Form pores and channels in the cell membrane, leading to cell death. - **Non-Membrane Targeting AMPs:** Directly act on intracellular targets, such as nucleic acids and proteins, by binding and disrupting their structure. **Benefits and Limitations:Antimicrobial peptides (AMPs) are short, cationic peptides found in various living organisms, including bacteria, plants, animals, and humans. They play a crucial role in the innate immune systems of these organisms by interacting with the cell membranes of pathogens such as viruses, bacteria, and fungi. AMPs can act against both Gram-positive and Gram-negative pathogens through various mechanisms, including membrane disruption, targeting intracellular organelles, and inhibiting nucleic acid and protein synthesis. This review focuses on AMPs from plants, animals, and humans, discussing their structures, modes of action, and potential applications. **Plants:** - **Structures:** Plant AMPs are typically cysteine-rich and form multiple disulfide bonds, giving them a compact structure. They include thionins, defensins, hevein-like peptides, knottins, α-hairpinins, lipid transfer proteins, snakins, and non-cysteine-rich peptides. - ** Modes of Action:** Plant AMPs can disrupt cell membranes, form pores, and interfere with intracellular processes. They have broad-spectrum activity against bacteria, fungi, and viruses. **Animals:** - **Structures:** Animal AMPs are categorized into defensins and cathelicidins. Defensins are cationic and composed of 29 to 42 amino acids with three pairs of disulfide bonds. Cathelicidins vary in size and structure but are positively charged and amphipathic. - ** Modes of Action:** Animal AMPs target both Gram-positive and Gram-negative bacteria. They can permeabilize cell membranes, inhibit protein synthesis, and disrupt intracellular pathways. **Humans:** - **Structures:** Human AMPs, primarily cathelicidins, include LL-37, cathelicidin 4 (indolocidin), protegrins, and histatins. They have antibacterial, antifungal, and antiviral activities. - ** Modes of Action:** Human AMPs can target viral envelopes, prevent viral binding to host cells, and interfere with viral replication. They also act on bacterial membranes and intracellular targets, such as nucleic acids and proteins. **Modes of Action and Mechanisms:** - **Antiviral AMPs:** Target viral envelopes, prevent viral binding to host cells, and interfere with viral replication. - **Antibacterial AMPs:** Interact with negatively charged bacterial membranes, causing membrane instability and disruption. - **Antifungal AMPs:** Similar to antibacterial AMPs, they target fungal cell walls and intracellular components. - **Membrane-Targeting AMPs:** Form pores and channels in the cell membrane, leading to cell death. - **Non-Membrane Targeting AMPs:** Directly act on intracellular targets, such as nucleic acids and proteins, by binding and disrupting their structure. **Benefits and Limitations: