The present invention relates to a novel protein having O-acetylhomoserine sulfhydrylase activity, a mutant protein thereof, a polynucleotide encoding the same, a recombinant vector comprising the polynucleotide, a microorganism transformed with the recombinant vector, and a method for producing methionine or acetic acid using the protein. The production method of the present invention has the advantage of producing L-methionine and acetic acid cost-effectively through having higher conversion rate and reduced reaction time compared to the existing methods, and it can minimize the amount of enzyme homogenate added when using the mutant protein, thereby easily producing L-methionine and acetic acid at high yield.