Beyond Glutathione: Different Low Molecular Weight Thiols as Mediators of Redox Regulation and Other Metabolic Functions in Lower Organisms

Abstract

Non-protein low molecular weight (LMW) thiols play an important role in the maintenance and regulation of a diverse array of cellular processes including redox maintenance, xenobiotic detoxification, and resistance to oxidative stress. Not all organisms, however, produce or utilize GSH. In particular, many Gram- positive bacteria produce other LMW thiols such as mycothiol, bacillithiol, trypanothione, and gamma-glutamylcysteine, which appear to serve as GSH surrogates. In addition to their major LMW thiol, many organisms also utilize additional thiol cofactors as redox buffers such as coenzymeA, ovothiol, and ergothioneine. This chapter provides a broad overview of what is currently known about these other LMW thiols which occur in numerous organisms besides, or instead of, GSH. Some of the LMW thiol discussed herein (e.g., bacillithiol) have only very recently been discovered, whereas the existence of others has long been known. Therefore, some perspective on future avenues of investigation that could provide a more comprehensive picture of their various metabolic functions is also provided.