The biosynthesis of MPT from cPMP. In the MPT synthase mechanism, cPMP is bound to the MoaE subunit. The initial attack and transfer of the first thiocarboxylated MoaD-SH sulfur atom occurs at the C2′ position of cPMP, coupled to the hydrolysis of the cPMP cyclic phosphate. An intermediate is formed in which the MoaD C-terminus is covalently linked to the substrate via a thioester linkage that is subsequently hydrolyzed by a water molecule to generate a hemisulfurated intermediate at C2′. Opening of the cyclic phosphate shifts the location of the intermediate within the complex to a position where C1′ becomes more accessible. A new MoaD-SH thiocarboxylate attacks the C1′ resulting in a second covalent intermediate which is converted to MPT via the elimination of a water molecule and hydrolysis of the thioester intermediate. During the reaction, cPMP remains bound to the MoaE molecule. The MPT synthase tetramer is built of two MoaE and two MoaD subunits. The MoaD-SH thiocarboxylate is formed on MoeB, where MoaD is first activated under ATP consumption to form an activated MoaD acyl-adenylate. Further, sulfur is transferred from a sulfur relay system by an L-cysteine desulfurase in conjunction with either TusA or YnjE to MoaD. The mechanism was adapted from the one proposed in [55].