Rapid Stimulation of protein carboxymethylation in leukocytes by a chemotactic peptide

Abstract

THERE has been considerable interest recently in protein carboxylmethyltransferase, and in its possible role in secretory¹ and chemotactic mechanisms^2,3. 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 pH to liberate methanol^6,7. The enzyme is widely distributed in mammalian tissues, especially in endocrine organs and brain^7,8. Escherichia coli and Salmonella typhimurium appear to require methylation for chemotaxis^2,3. 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.