Sortases are Gram-positive bacteria extracellular transpeptidase enzymes responsible for covalently attaching secreted proteins to the peptidoglycan cell wall. The name of the enzymes derived from the role the enzymes play in the protein sorting pathway, ‘sorting’ proteins into the cell wall compartment of Gram-positive bacteria. The peptidoglycan is composed of numerous glycan polymers made up of repeating chains of N-acetyl glucosamine and N-acetylmuramic acid which are cross linked to one another by peptide stems. The peptide stems are generally composed of five amino acids with an inter-peptide branch at position 3. Staphylococcus aureus comprises L-Ala-D-iGlu-L-Lys-DAla- D-Ala with a pentaglycine inter-peptide branching off the L-Lys. These peptide cross-links between the glycan strands vary between Gram-positive and Gram negative bacteria in the inter peptide branching region. Based on the primary sequences around 60% of sortase homologues in Gram-positive bacteria can be clustered into six families but class A and class B sortase enzyme studied in details. Sortase have important role in displaying virulence factors of bacterium which makes them promising drug targets. Class -specific structural features important for molecular basis of substrate recognition. Inhibition of sortase enzyme activity can decrease the virulence of some pathogenic bacteria so sortases are considered as targets for antibacterial drugs and development of new generation of antibiotics against very virulent bacterial species. Sortase enzymes utilized for development of biofilm vaccine, capsular and flagellar vaccine and mutagenic strains have wide industrial application.
