Catalyzes the dehydration of methylthioribulose-1-phosphate (MTRu-1-P) into 2,3-diketo-5-methylthiopentyl-1-phosphate (DK-MTP-1-P). Dephosphorylates 2-hydroxy-3-keto-5-methylthiopentenyl-1-phosphate (HK-MTPenyl-1-P) yielding 1,2-dihydroxy-3-keto-5-methylthiopentene (DHK-MTPene). S-methyl-5-thio-D-ribulose 1-phosphate = 5-methylsulfanyl-2,3-dioxopentyl phosphate + H2O 2-hydroxy-5-methylsulfanyl-3-oxopent-1-enyl phosphate + H2O = 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one + phosphate Binds 1 zinc ion per subunit. Amino-acid biosynthesis; L-methionine biosynthesis via salvage pathway; L-methionine from S-methyl-5-thio-alpha-D-ribose 1-phosphate: step 2/6. Amino-acid biosynthesis; L-methionine biosynthesis via salvage pathway; L-methionine from S-methyl-5-thio-alpha-D-ribose 1-phosphate: step 4/6. Homotetramer. In the N-terminal section; belongs to the HAD-like hydrolase superfamily. MtnX family. In the C-terminal section; belongs to the aldolase class II family. MtnB subfamily.