A heterodimeric protein complex which catalyses sulfur transfer from the sulfur carrier subunit of MPT synthase to precursor Z to synthesize MPT as part of molybdopterin cofactor (Moco) biosynthesis. In E. coli the subunits are MoaE and MoaD; in human, MOCS2B and MOCS2A. Moco biosynthesis and its constituent molecules are evolutionarily conserved.