A series of phosphoric, phosphonic and phosphinic acid mimics of the N7DAPA-carbamate were prepared and analyzed as inhibitors and alternate substrates for DTBS. Extension of the phosphorous moiety by a methylene spacer resulted in weaker inhibition at high ATP levels suggesting that the phosphorous group was overlapping with the 7 -phosphate of ATP rather than the carbamate carboxyt site. This was confirmed by the crystal structure of 7-( 1-hydroxyethyl)-9-phosphonononanoic acid (KU843) complexed with the enzyme. In general, phosphorous-containing inhibitors that were dianionic showed weaker inhibition at high ATP levels as did inhibitors that did not have amino groups at the position equivalent to the N8-position of the DAPA carbamate. Most of the phosphorous-containing inhibitors were slowly phosphorylated in the presence of MgATP since ADP was released, but not phosphate. The transfer of phosphate from MnATP to 7-(1-aminoethyl)(methylphosphino)-octanoic acid (MG026) was observed in the crystal structure of the complex of DTBS with this inhibitor and MnATP. Unlike glutamine synthetase, glutathione synthetase, and glutamylcysteine synthetase, where potent inhibition was observed with phosphinic acid inhibitors that become mimics of acyl-phosphate intermediates upon phosphorylation, the carbamate mimics presented here were relatively weak (uM) inhibitors of DTBS.
|Original language||English (US)|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Molecular Biology