Antimicrobial proteins are proteinaceous components of innate host defense that directly impair the survival, growth, colonization, or infectivity of microorganisms. Within the taxonomy of antimicrobial peptides and activities, the term encompasses both relatively large proteins and their bioactive peptide products when these molecules possess intrinsic antimicrobial activity. Their targets include bacteria, fungi, viruses, and parasites, although the spectrum and magnitude of activity depend on the molecular structure of the protein, the target organism, and the local physicochemical environment ^[1][2].

Antimicrobial proteins act through diverse molecular mechanisms. These include disruption or permeabilization of microbial envelopes; enzymatic degradation of microbial structural components; sequestration of nutrients required for microbial growth, particularly metal ions; binding to microbial surface molecules; interference with intracellular microbial processes; and modulation of host immune responses that contribute to microbial control ^[2][3][4]. They are therefore distinguished from conventional low-molecular-weight antimicrobial drugs by their protein or peptide composition and by the frequent integration of direct microbicidal or microbiostatic effects with host-defense functions. Antimicrobial peptides constitute a structurally shorter subset of this broader proteinaceous defense system, whereas antimicrobial proteins may retain activity as intact macromolecules or release active peptide fragments after proteolytic processing ^[1][4].