Molybdopterin synthase

K V. Mechanistic and mutational studies of Escherichia coli molybdopterin synthase clarify the final step of molybdopterin biosynthesis,... 

Rudolph, M. J., Wuebbens, M. M., Rajagopalan, K. V., and Schindelin, H. Crystal structure of molybdopterin synthase and its evolutionary relationship to ubiquitin activation,... 

What is known about the biosynthesis of MPT and the MPT dinucleotides has been reviewed elsewhere from both a biochemical and a genetic perspective [7,8,62-64], Here we only discuss the hnal steps in MPT biosynthesis, which involve the enzyme molybdopterin synthase [65,66],... 

Molybdopterin synthase is a 27 kDa protein (in its inactive resting state) that is comprised of 16 and 10 kDa subunits [67], The protein has a tendency to dissociate and the exact stoichiometry of the active synthase remains uncertain. Activation of the protein requires that the smaller subunit undergo a single sulfur-for-oxygen exchange, a finding that has been confirmed by mass spectral analysis of both active and inactive 10 kDa subunits. Since conversion of the precursor to MPT requires two sulfur atoms, it has been postulated that the active form of the synthase contains two 10 kDa subunits [67], The synthase not only provides sulfur atoms for MPT precursor conversion but also transports MPT to the apo-molybdenum (or presumably apotungsten) enzyme. 

Whereas the triester reacts with a range of sulfur nucleophiles, the corresponding diester does not react with thionucleophiles under ambient conditions (Eq. 8), suggesting that the precursor, which is a diester, must be activated for conversion to MPT. This activation could involve the C3 hydroxyl group of the precursor, which is missing in the model, or Lewis acidic groups present in molybdopterin synthase. 

The properties of CODH/acetyl-CoA synthase are summarized in Table II. The enzyme has been isolated from eight species. There exist three types of CODH. One, which lacks nickel and acetyl-CoA synthase activity, contains a molybdopterin active site and will not be... 

The Thil gene, which encodes aother sulfurtransferase protein, is also needed.3743 The enzymology of the insertion of this sulfur into the thiazole is uncertain but may resemble that involved in synthesis of biotin, lipoic acid, and molybdopterin.374 Linkage of the two parts of the thiamin molecule (step d, Fig. 25-21) is catalyzed by thiamin phosphate synthase, evidently via an SN2 type reaction.377-37713... 

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