Methanethiol and dimethylsulfide formation from 3-methylthiopropionate in human and rat hepatocytes

This study was designed to investigate the metabolism of methanethiol, and the involvement of methanethiol and its metabolites in the transamination pathway of methionine. Gaseous methanethiol, methanethiol-mixed disulfides and dimethylsulfide were formed from 3-methylthiopropionate, a metabolite in the transamination pathway of methionine, during incubation with human and rat hepatocytes. An increase of the 3-methylthiopropionate concentration resulted in an increased formation of the products, up to a substrate concentration of 4.4 mM. Higher substrate levels resulted in a decreased methanethiol formation, probably due to poisoning of the system. However, in human hepatocytes the formation of dimethylsulfide increased up to a 3-methylthiopropionate concentration of 12.5 mM. The formation of methanethiol, dimethylsulfide and methanethiol-mixed disulfides from 3-methylthiopropionate in hepatocytes of both human and rat support the hypothesis that methanethiol can be formed from methionine via the transamination pathway.