N-formyl-L-methionine is a L-methionine derivative in which one of the hydrogens attached to the nitrogen is replaced by a formyl group. It has a role as a metabolite. It is a proteinogenic amino acid, a N-formyl amino acid and a L-methionine derivative. It is a conjugate acid of a N-formyl-L-methioninate. N-Formyl-L-methionine belongs to the class of organic compounds known as methionine and derivatives. Methionine and derivatives are compounds containing methionine or a derivative thereof resulting from reaction of methionine at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom. N-Formyl-L-methionine is effective in the initiation of protein synthesis. The initiating methionine residue enters the ribosome as N-formylmethionyl-tRNA. This process occurs in Escherichia coli and other bacteria as well as in the mitochondria of eukaryotic cells. Polymorphonuclear cells can bind proteins starting with fMet, and use them to initiate the attraction of circulating blood leukocytes and then stimulate microbicidal activities such as phagocytosis. Since fMet is present in proteins made by mitochondria and chloroplasts, more recent theories do not see it as a molecule that the immune system can use to distinguish self from non-self. Instead, fMet-containing oligopeptides and proteins appear to be released by the mitochondria of damaged tissues as well as by damaged bacteria, and can thus qualify as an "alarm" signal, as discussed in the Danger model of immunity. The prototypical fMet-containing oligopeptide is N-formylmethionine-leucyl-phenylalanine (FMLP) which activates leukocytes and other cell types by binding with these cells' formyl peptide receptor 1 (FPR1) and formyl peptide receptor 2 (FPR2) G protein coupled receptors (see also formyl peptide receptor 3). Acting through these receptors, the fMet-containing oligopeptides and proteins are part of the innate immune system; they function to initiate acute inflammation responses but under other conditions function to inhibit and resolve these responses. fMet-containing oligopeptides and proteins also function in other physiological and pathological responses. fMet is a starting residue in the synthesis of proteins in bacteria, and, consequently, is located at the N-terminus of the growing polypeptide. The addition of the formyl group to methionine is catalyzed by the enzyme methionyl-tRNA formyltransferase. This modification is done after methionine has been loaded onto tRNAfMet by aminoacyl-tRNA synthetase. The mitochondria of eukaryotic cells, including those of humans, and the chloroplasts of plant cells also initiate protein synthesis with fMet. Given that mitochondria and chloroplasts have this initial protein synthesis with fMet in common with bacteria, this has been cited as evidence for the endosymbiotic theory. Protein synthesis in mitochondria is initiated by formylmethionyl-tRNAMet (fMet-tRNAMet), which requires the activity of the enzyme MTFMT to formylate the methionyl group. The conversion of methionine to N-N-Formyl-L-Methionine (L-methionyl-tRNAMet) is completed in the mitochondria by Methionine--tRNA ligase (MARS2). This reaction is as follows: ATP + L-methionine + tRNA(Met) = AMP + diphosphate + L-methionyl-tRNA(Met).

Metabolism and Physiological Effects of N-Formyl-L-Methionine References