Automated sample preparation with 6-Aminoquinolyl-N-hydroxysuccinimidyl carbamate and iodoacetamide derivatization reagents for enantioselective liquid chromatography tandem mass spectrometry amino acid analysis

Enantioselective amino acid analysis is gaining increasing importance in pharmaceutical, biomedical and food sciences. While there are many methods available for enantiomer separation of amino acids, the simultaneous analysis of all chiral proteinogenic amino acids by a single method with one column and a single condition is still challenging. Herein, we report an enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS) assay using Chiralpak QN-AX as chiral column. With 6-aminoquinolyl-N-hydrosysuccinimidyl carbamate (AQC) as derivatization reagent, efficient enantioselective separation of D- and L-amino acids using HPLC has become possible. Thiol-containing amino acids like Cys are alkylated prior to AQC-labelling. A protocol for automated sample preparation including both derivatization step and calibrator preparation is presented. For compensating matrix effects, u-13C15N-labelled internal standards (IS) were employed. The method was validated and applied to the enantioselective analysis of amino acids in a bacterial fermentation broth.

Development of a novel single-chain l-glutamate oxidase from Streptomyces sp. X-119-6 by inserting flexible linkers

L-glutamate oxidase (LGOX, EC: 1.4.3.11) is an oxidoreductase that catalyzes L-glutamate deamination. LGOX from Streptomyces sp. X-119-6 is used widely for L-glutamate quantification in research and industrial applications. This enzyme encoded as a single precursor chain that undergoes post-translational cleavage to four fragments by an endogenous protease to become highly active. Efficient preparation of active LGOX by heterologous expression without proteolysis process should be indispensable for wide application of this enzyme. Thus, developing an LGOX that requires no protease treatment should expand the potential applications of recombinant LGOX. In this report, we succeeded in obtaining an active single-chain LGOX by connecting the four fragments of the mature form with insertion of flexible linkers. The most active single-chain mutant showed the similar activity to that of the mature form from Streptomyces sp. X-119-6. The structure of this mutant was determined at 2.9 Å resolution by X-ray crystallography. It was revealed that this single-stranded mutant had the similar conformation to that of mature form. This single-chain LGOX can be produced efficiently and should expand LGOX applications.

CE-MS for the Analysis of Amino Acids

Amino acids play an important role in clinical analysis. Capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) has proven to possess several characteristics that make it a powerful and useful tool for the analysis of amino acids in clinical studies. Here we present a method for the separation and quantitative analysis of 27 amino acids in urine based on CE-ESI-MS. The method presents an improved resolution between the isomers Leu, Ile, and aIle, in comparison to other CE-ESI-MS methods in the literature. This method is fast, selective, and simple and has improved sensitivity by applying a pH-mediated stacking strategy, showing that it can be successfully used for amino acid analysis and probably for other small cationic metabolites.

Comparison of cake compositions, pepsin digestibility and amino acids concentration of proteins isolated from black mustard and yellow mustard cakes

As a byproduct of oil production, black and yellow mustard cakes protein are considered as potential source of plant protein for feed applications to poultry, fish and swine industries. The protein contents in black and yellow mustard cakes were 38.17% and 28.80% and their pepsin digestibility was 80.33% and 77.43%, respectively. The proteins were extracted at different pH and maximum proteins (89.13% of 38.17% and 87.76% of 28.80% respectively) isolated from black and yellow mustard cakes at pH 12. The purity of isolated proteins of black and yellow mustard cakes was 89.83% and 91.12% respectively and their pepsin digestibility was 89.67% and 90.17% respectively which assigned the absence of antinutritional compounds. It was found that essential amino acids isoleucine, lysine, methionine, threonine and tryptophan and non essential amino acids arginine and tyrosine were present in greater concentration in black mustard cake protein whereas other amino acids were higher in yellow mustard cake protein.