fiveglycine

Fiveglycine, more commonly called pentaglycine, is a term that may refer to a peptide chain composed of five glycine residues (Gly-Gly-Gly-Gly-Gly). In a chemical sense, it is the glycine pentamer linked by four peptide bonds, resulting in a flexible, linear chain with free amino and carboxyl termini. In microbiology, pentaglycine is often used to describe the five-residue cross-bridge that links stem peptides in the peptidoglycan of certain bacteria, most notably Staphylococcus aureus.

The pentaglycine cross-bridge is synthesized by enzymes of the Fem family (such as FemX, FemA, and FemB) that sequentially add glycine residues to a carrier molecule before incorporation into the cell wall. The length and composition of this cross-bridge influence the degree of cross-linking, cell wall rigidity, and antibiotic susceptibility profiles of the organism.

In the laboratory, pentaglycine can be produced by standard solid-phase peptide synthesis and used as a model substrate for studies of peptidoglycan assembly, cross-linking chemistry, and enzyme mechanisms involved in cell wall biosynthesis. It is not a marketed drug or a widely used reagent outside of research contexts.

See also: peptidoglycan, glycine, pentapeptide.