Degradation kinetics of l-glutamine in aqueous solution

Roles of N-terminal Pyroglutamate in Maintaining Structural Integrity and pKa Values of Catalytic Histidine Residues in Bullfrog Ribonuclease 3

“…Furthermore, the resulting Gln1 was converted into Pyr1 non-enzymatically after refolding in phosphate buffer. 14,30 Similarly, the production of recombinant protein starting with Pyr1 was performed for other frog ribonucleases, but with different efficiency of Pyr1 formation; for example, those of onconase, RC-RNase 3 and RC-RNase L1 are similar to each other, while that of RC-RNase 2 is lower than RC-RNase 3 (unpublished results in this laboratory). Thus, the method we developed is able to prepare sufficient amount of recombinant proteins with an innate N terminus rather than using a Met-tagged protein for studying the role of the N-terminal residue on the function and structure of these proteins, e.g.…”

“…13 The former is performed only if no internal Met is present in the primary sequence and the latter method requires purified protein substrate and protease. Furthermore, the N-terminal glutaminyl residue (Gln1) should be converted into a Pyr1 residue under non-enzymatic condition, 14 or with acceleration by the glutamine cyclase, 15 for the function of the protein. In this study, a pelB signal peptide was introduced in front of the N-terminal Gln1 of RC-RNase 3 and removed completely in an Escherichia coli expression system.…”

Direct determination of amino acids by hydrophilic interaction liquid chromatography with charged aerosol detection

“…It was also observed that chromatographically, the glutamine peak had correspondingly decreased by ~15%; while no other analytes appeared to have changed. The likely degradation of glutamine into 5-pyrrolidone-2-carboxylic acid (pGlu) is due to the acidic environment of the diluent [51]. Injection of authentic pGlu material confirmed the identification by matching retention time.…”

Stability of Minimum Essential Medium functionality despite l-glutamine decomposition

“…L-Gln has been recognized as the principal source of nascent ammonia. L-Gln is labile in solutions (including culture media) and degrades spontaneously through cyclization generating pyroglutamic acid and ammonia as byproduct (Tritsch and Moore 1962;Heeneman et al 1993;Arii et al 1999). Additionally, metabolic degradation of L-Gln also generates ammonia, as well as glutamate, alanine and aspartate.…”