Cellular responses to serine in yeast.

The serine-glycine interconversion has been the subject of considerable research over several decades and it involves series of reactions of relevance to bacteria and fungi as well as higher organisms. Much has been published on the role of cofactors and one-carbon units in this reversible relationship. Current studies are aimed at understanding the regulation and the overall systems biology of the synthesis of serine and glycine and their roles in one-carbon metabolism (and hence methylation reactions), in the synthesis of other important metabolites critical for DNA replication, in membrane lipid synthesis and amino acid synthesis, in oxidative and heat stress responses, and also as sources of nitrogen, as exemplified by evidence obtained with yeast (Saccharomyces cerevisiae). The transcriptional and metabolic responses of yeast to added serine and glycine are discussed. It should be noted that serine can be synthesized from a variety of sources, including glycolysis via 3-phosphoglycerate and threonine via threonine aldolase, which converts threonine to acetaldehyde and glycine, the latter being the precursor of serine through the action of the glycine decarboxylase complex.