Chemical and Biochemical Studies of Bacillithiol

Abstract

Bacillithiol (BSH), the α-anomeric glycoside of L-cysteinyl-D-glucosamine with L-malic acid, is the recently identified low-molecular-weight (LMW) thiol in low G + C content Gram-positive bacteria. Although BSH has not been fully characterized it is thought to have functions analogous to those of glutathione, the major LMW thiol present in eukaryotes. Glutathione is known to act as an antioxidant and functions to protect the cell against oxidation and other toxins. BSH has been shown to contribute to the detoxification of toxic compounds including some antibiotics. Since bacillithiol is not present in humans its metabolism presents novel targets for antibacterial drug therapies. An attempt was made to chemically synthesize BSH for its use in biochemical studies that would further elucidate its functions. The trichloroacetimidate method was employed for the introduction of the α-glycosidic bond linking D-glucosamine with an L-malic acid derivative. A cysteine derivative was prepared with a pentafluorophenyl group activating it for peptide bond formation with D-glucosamine. NMR and IR spectroscopy were used to confirm the synthesis of these compounds. Efforts made toward forming the peptide bond without the use of a peptide coupling reagent were unsuccessful.