[Minor peptides of animal proteins as antibiotics and possible factors of nonspecific immunity].

Screening of more than twenty short synthetic peptides characteristic of different proteins has revealed antimicrobial activity of the KRFAE peptide--from human preproenkephalin A against gram-negative bacteria. Modification of the peptide structure by means of administration of d-amino acids has permitted obtaining dKRFdLE analogue with the expressed and stable antimicrobial activity in vitro when growing bacteria on the minimum glucose-mineral medium. Changes and rearrangements of aminoacids in the dKRFdLE peptide in the second, third and fourth positions sharply decreased anti-microbial activity. The weaker antimicrobial activity as compared with that in dKRFdLE was peculiar to peptides with the other primary structure. Possible participation of peptides as antibiotics in the mechanisms of nonspecific immunity as well as the methods of their rational search are discussed.