Applicability of the phosphorus-31 (oxygen-17) nuclear magnetic resonance method in the study of enzyme mechanism involving phosphorus.

The phosphorus-31 (oxygen-17) [31P (17O)] NMR method [Tsai, M.-D. (1979) Biochemistry 18, 1448-1472] is tested for its general applicability by correlation with the line widths of the 17O NMR signals for the following compounds: trimethyl [17O4]phosphate (1), [17O4]phosphate (2), [alpha-17O2]adenosine 5'-(thiophosphate) (3), [alpha-17O, alpha beta-17O]-adenosine 5'-(1-thiotriphosphate) (4) [gamma-17O3]adenosine 5'-triphosphate (5), [alpha beta, beta gamma-17O2, beta-17O2]adenosine 5'-triphosphate (6), magnesium [gamma-17O3]adenosine 5'-triphosphate (7), and magnesium [alpha beta, beta gamma-17O2, beta-17O2]adenosine 5'-triphosphate (8). It is found that the line broadening effect of 17O on the 31P signals of the directly bonded 31P nuclei is present for all the functional groups in the above compounds which include examples of small 17O line widths (1 and 2), of intermediate 17O line widths (3, 5, and the nonbridge 17O of 4 and 6), and of very large 17O line widths (7, 8, and the bridge 17O of 4 and 6). On the basis of the established approximate relationship delta chi delta Q approximately aJ2, where delta chi and delta Q are the 31P and 17O line widths, respectively, of the 31P-17O groups, alpha is a constant, and J is the 31P-17O coupling constant, the results suggest that for most of the phosphate derivatives of biochemical interest, the line broadening effect of 17O should be present and detectable; i.e., delta chi should be larger than the limiting value (approximately 20 Hz). It is also found that Mg2+ causes the 17O signal of 5 and 6 to broaden (delta Q increases), which in turn causes the 31P signal to sharpen (delta chi decreases). The finding suggests that the 31P (17O) NMR methods, in combination with 17O NMR, could become a tool to study diamagnetic metal ion-nucleotide interactions.