The function of TMT1B (thiol methyltransferase 1B, Ensembl gene identifier ENSG00000170439) is as follows. Thiol S-methyltransferase that catalyzes the transfer of a methyl group from S-adenosyl-L-methionine to alkyl and phenolic thiol- containing acceptor substrates. Together with TMT1B accounts for most of S-thiol methylation activity in the endoplasmic reticulum of hepatocytes. Selectively methylates S-centered nucleophiles from metabolites such as hydrogen sulfide and dithiothreitol. .