Enzyme-bound intermediates in the conversion of glucose 1-phosphate to glucose 6-phosphate by phosphoglucomutase. Phosphorus NMR studies

摘要: The interactions between metal ions and the phospho form of rabbit muscle phosphoglucomutase (EC 2.7.5.1) have been studied by 31P NMR. In metal-free enzyme, width at half-height signal is 10 +/- 1 Hz 81 MHz. enzyme-Cd2+ complexes, presence spin-spin coupling with 113Cd2+ (J113Cd-O-31P = 16 Hz) absence such splitting 114Cd2+ indicate that Cd2+ binds directly to enzymic phosphate. detectable on transfer phosphate group acceptor hydroxyl bound glucose 1-phosphate, or 6-phosphate (to give complex dephospho-enzyme 1,6-bisphosphate), indicates this eliminates direct ion-phosphate interaction. enzyme-catalyzed reaction slowed sufficiently addition Li+ allow studies three discrete intermediate complexes NMR techniques: 1-phosphate phosphoenzyme, 1,6-bisphosphate dephosphoenzyme (only one type was observed), phosphoenzyme. Complete assignments phosphorus resonances these intermediates made labeling ester either enzyme sugar 17O polarization studies. effect also determined. A titration study a experiment beta-glucose less tightly than alpha-glucose 1,6-bisphosphate.(ABSTRACT TRUNCATED AT 250 WORDS)