Syntheses of (2S,3R)- and (2S,3R)[3-2h]- 3-methylaspartic acid: slow substrates for a syn-elimination reaction catalysed by methylaspartase.
作者:Catherine H. Archer、Neil R. Thomas、David Gani
DOI:10.1016/s0957-4166(00)80221-9
日期:1993.6
Mediylaspartase catalyses the slow syn-elimination of ammonia from the (2S,3R)-[L-erythro]-diastereomer of the natural substrate, (2S,3S)-3-methylaspartic acid, to give mesaconic acid. To provide material of sufficient stereochemical purity to probe the mechanism of the reaction, two synthetic routes to (2S,3R)- and (2S,3R)[3-H-2]- 3-methylaspartic acid were devised. The use of these (2S,3R)-3-methylaspartic acids revealed that the enzymic reaction does not involve C-3 epimerisation followed by normal anti-elimination, ruling-out the possibility of a carbanion intermediate. Conversely, the substrate displayed very large primary deuterium isotope effects indicating rate-limiting C-H bond cleavage.
Mapping the Aspartic Acid Binding Site of <i>Escherichia coli</i> Asparagine Synthetase B Using Substrate Analogs
作者:Ian B. Parr、Susan K. Boehlein、Anthony B. Dribben、Sheldon M. Schuster、Nigel G. J. Richards
DOI:10.1021/jm9601009
日期:1996.1.1
Novel inhibitors of asparagine synthetase, that will lower circulating levels of blood asparagine, have considerable potential in developing new protocols for the treatment of acute lymphoblastic leukemia. We now report the indirect characterization of the aspartate binding site of Escherichia coli asparagine synthetase B (AS-B) using a number of stereochemically, and conformationally, defined aspartic