Catalyzes the formation of L-homocysteine from O-succinyl-L-homoserine (OSHS) and hydrogen sulfide. hydrogen sulfide + O-succinyl-L-homoserine = L-homocysteine + succinate Binds 1 pyridoxal phosphate per subunit. Amino-acid biosynthesis; L-methionine biosynthesis via de novo pathway; L-homocysteine from O-succinyl-L-homoserine: step 1/1. Homotetramer. Belongs to the trans-sulfuration enzymes family. MetZ subfamily.