RAPID STIMULATION OF PROTEIN CARBOXYMETHYLATION IN LEUKOCYTES BY A CHEMOTACTIC PEPTIDE

There has been considerable interest recently in protein carboxylmethyltransferase, and in its possible role in secretory1 and chemotactic mechanisms2,3. Using S-adenosyl-L-methionine as the methyl donor, this enzyme catalyses the formation of protein methyl esters 4,5 which undergo rapid spontaneous hydrolysis at physiological p H to liberate methanol6,7. The enzyme is widely distributed in mammalian tissues, especially in endocrine organs and brain7,8. Escherichia coli and Salmonella typhimurium appear to require methylation for chemotaxis2,3. Eukaryotic cells, such as leukocytes (neutrophils, polymorphonuclear cells), have been shown to respond chemotactically to a variety of peptides derived from complement9, to crude bacterial factors10, and more recently to welldefined synthetic formylated peptides11. We wish to report here the presence in leukocytes of a protein carboxylmethyltransferase system, whose activity is specifically stimulated by synthetic peptides, which may be related to chemoattractants produced by bacteria12. © 1978 Nature Publishing Group.