1. Mass spectrometric and kinetic studies on slow progression of papain-catalyzed polymerization of L-glutamic acid diethyl ester
Asako Narai-Kanayama, Hiroyuki Koshino, Keiichi Aso Biochim Biophys Acta. 2008 Jun;1780(6):881-91. doi: 10.1016/j.bbagen.2008.03.009. Epub 2008 Mar 20.
Papain polymerizes L-glutamic acid diethyl ester (Glu-di-OEt) regioselectively, resulting in the formation of poly (gamma-ethyl alpha-L-glutamic acid) with various degrees of polymerization of less than 13. Reaction temperatures below 20 degrees C were appropriate for the reaction in terms of suppression of non-enzymatic degradation of Glu-di-OEt and an increase in the peptide yield, while the reaction was preceded by a pronounced induction period. Mass spectrometric analyses of the reaction conducted at 0 degrees C revealed that the accumulation of the initial dimerization product, L-glutamyl-L-glutamic acid triethyl ester (Glu-Glu-tri-OEt), was limited during the induction period, and that a sequential polymer derived from a further elongation of the dimer was the tetramer, but not the trimer. Kinetic analyses of acyl transfer reactions with Glu-di-OEt and Glu-Glu-tri-OEt as acyl acceptors and Nalpha-benzoyl-L-arginine ethyl ester as an acyl donor affirmed that Glu-Glu-tri-OEt bound more strongly than Glu-di-OEt both to the S- and S'-subsites of papain. Therefore, what occurred during the initial stage of the polymerization was interpreted as follows: the rate of the papain-catalyzed dimerization of Glu-di-OEt was extremely slow, once Glu-Glu-tri-OEt was initially synthesized it exclusively bound to the active site of papain, and then papain utilized the dimer in polymerization effectively rather than the monomer.
3. [Anti-ammonemic activity of the gamma-ethyl ester of glutamic acid. Controlled clinical study]
G Santagati, G Zibetti, F Forgione, A Spaghi Minerva Med. 1979 Feb 18;70(8):595-603.
A controlled clinical trial was made of the anti-ammoniaemic properties of gamma-ethylester glutamic acid, arginine and placebo in a series of 45 patients with hepatic insufficiency characterized by hyperammonemia (excluding cases of pre-coma and coma) randomly assigned to three groups for treatment with: gamma-ethylester of glutamic acid (25 g), l-arginine (25 g) and physiological solution in identical 500 ml bottles. Various parameters were controlled. The results obtained were assessed with different statistical techniques, depending on the parameter concerned and the aims of the trial. Blood ammoniaemia was significantly decreased by both-ethylester of glutamic acid and arginine though the former was more effective quantitatively and in terms of time. SGOT and BSF values also followed the same pattern.
