13C NMR and 1H-1H NOEs of Coenzyme-A: Conformation of the Pantoic Acid Moiety

The 3″-hydroxyl group of the pantetheine moiety of coenzyme-A generates diastereotopic methyl groups and protons at the 2″- and 1″-carbons, respectively. An analysis of the available crystal structures of coenzyme-if complexed at enzyme active sites suggests a common conformation for the pantoic acid portion of pantetheine. In this conformation, the preferred conformations about the O(1″)-C1″ bond is anti, about the C1″-C2″ bond gauche, and about the C2″-C3″ anti. The reported 1H-1H nuclear Overhauser enhancements between these protons are consistent with the observed crystal structure conformations and facilitate the assignments made to the diastereotopic resonances. A HeteroCOSY spectrum allowed an unequivocal and complete assignment of the 13C NMR for coenzyme-A, resolving the discrepancies between the assignments made by Roeder et al. (Physiol. Chem. Phys.7, 115-122 (1975)) and Patel and Walt (Anal. Biochem.170, 355-360 (1988)).