Cysteine Synthase: Characteristics of the Main Enzyme in the Cysteine Synthetic Pathway

Cysteine is an extremely important amino acid for the normal functioning of living organisms. In bacteria and plants, the main route of cysteine synthesis is the thioylation pathway, the second stage of which is provided by either cysteine synthase A (CysK) if the substrate is inorganic sulfide, or cysteine synthase B (CysM) if the substrate is thiosulfate. The crucial role of these enzymes in the synthesis of cysteine makes them promising targets of antimicrobial agents for the treatment of infectious diseases, the creation of new herbicides, as well as in the industrial production of cysteine. However, besides of the main functions, the additional activity of these enzymes is of interest, such as their use as antimicrobial or antibiotic film agents. This review examines the physico-chemical characteristics of CysK and CysM, discusses their diversity and potential applications in biotechnology and medicine.