Catalyzes the alpha,gamma-elimination of L-methionine to produce methanethiol, 2-oxobutanoate and ammonia (PubMed:8586629, PubMed:6742420). Is involved in L-methionine catabolism (PubMed:9190812). In fact, shows a multicatalytic function since it also catalyzes gamma-replacement of L-methionine with thiol compounds, alpha,gamma-elimination and gamma-replacement reactions of L-homocysteine and its S-substituted derivatives, O-substituted-L-homoserines and DL-selenomethionine, and, to a lesser extent, alpha,beta-elimination and beta-replacement reactions of L-cysteine, S-methyl-L-cysteine, and O-acetyl-L-serine (PubMed:6742420, PubMed:22785484). Also catalyzes deamination and gamma-addition reactions of L-vinylglycine (PubMed:6742420). Thus, the enzyme is able to cleave C-S, C-Se, and C-O bonds of sulfur, selenium, and oxygen amino acids, respectively (PubMed:6742420, PubMed:22785484). H2O + L-methionine = 2-oxobutanoate + methanethiol + NH4(+) H2O + L-homocysteine = 2-oxobutanoate + H(+) + hydrogen sulfide + NH4(+) Irreversibly inactivated by DL-propargylglycine. kcat is 33.4 sec(-1) for the alpha,gamma-elimination of L-methionine. kcat is 71.0 sec(-1) for the alpha,gamma-elimination of DL-homocysteine. kcat is 2.13 sec(-1) for the alpha,beta-elimination of L-cysteine. kcat is 1.58 sec(-1) for the alpha,beta-elimination of S-methyl-L-cysteine. kcat is 2.56 sec(-1) for the alpha,gamma-elimination of O-succinyl-L-homoserine. Homotetramer; dimer of active dimers. Is under the control of the positive transcriptional regulator MdeR. Forms part of an operon with mdeB. The recombinant MGL protein cloned form P.putida has been found to have antitumor efficacy in vitro and in vivo. PEGylated MGL is being developed as a cancer drug. Belongs to the trans-sulfuration enzymes family. L-methionine gamma-lyase subfamily.