The present invention relates to compositions and methods for determining the absolute configuration of D/L-cysteine and/or the enantiomeric composition of cysteine and/or the concentration of total cysteine in a sample. Uses of the composition and method are also described.

The present disclosure provides a method for detecting L-serine based on cysteine desulfurase-containing living Escherichia coli cells, and belongs to the technical field of amino acid detection. The method includes the following steps: incubating an unknown sample with the cysteine desulfurase-containing living E. coli cells to produce a red substance, and qualitatively or semi-quantitatively detecting L-serine content in the unknown sample according to color changes of the red substance of the living E. coli cells, or quantitatively detecting L-serine content in the unknown sample by measuring absorbance of a lysate of the living E. coli cells. The detection method provided by the present disclosure is simple and convenient in process, few in reaction steps and stable in enzymatic activity of living cells.

A biomarker panel for a urine test for detecting lung cancer detects a biomarker selected from the group of biomarkers consisting of DMA, C5:1, C10:1, ADMA, C5-OH, SDMA, and kynurenine, or a combination thereof. A biomarker panel for a serum test for detecting lung cancer detects a biomarker selected from the group of biomarkers consisting of valine, arginine, ornithine, methionine, spermidine, spermine, diacetylspermine, C10:2, PC aa C32:2, PC ae C36:0, and PC ae C44:5; and lysoPC a C18:2, or a combination thereof.

Disclose are methods, compositions and kits for the determination of kidney function that provide an alternative to the standard-of-cure used for eGFR calculations. Described herein are methods for quantitative measurement of ADMA and hydration markers in a urine sample, and process used to transform the input of these methods into a measure of kidney function. The methods allow ADMA and other biomarkers to be detected in urine samples from a subject using a simple and inexpensive assay that can be easily performed noninvasively and only require urine samples for the prediction of kidney function.

The present invention features a method comprising a metabolomic biomarker panel representing a metabolomic profile/fingerprint and methods of applying the profile to diagnose, monitor, and guide treatment for PAH. The profile comprises a unique panel of 36 metabolomic biomarkers/metabolites detected in plasma and/or urine obtained from the patient. The present invention allows for identification of patients with PAH in early-stage disease, before the condition has progressed sufficiently to produce clinical symptoms, and uniquely distinguishes PAH from pulmonary hypertension due to type 2 Diabetes Mellitus (DM) and/or left heart disease. The present invention allows for pre-screening of patients to identify PAH at the asymptomatic stage or help to minimize the time for PAH diagnosis after initial symptom onset.

A method of diagnosis of histamine intolerance in a person suspected of suffering from histamine intolerance syndrome. Isotope-labeled histamine metabolites, namely imidazole acetic acid and methylimidazole acetic acid are identified and measured in serum, plasma, urine and other bodily fluids following derivatization with a hydrazinoquinoline derivatization agent using the LC-MS/MS technique. The method and analytical technique is very sensitive and allows a safe use of an isotope-labeled oral histamine load as well as time-dependent measurements of the total activity of secreted and membrane-associated DAO enzymes for the sake of a differential diagnosis of histamine intolerance syndrome compared to food allergy, food hypersensitivity or food intolerance.

A method for the in situ derivatization of at least one biogenic amine, precursor, or metabolite thereof in an isolated aqueous sample includes the steps of: (i) contacting the sample with a propionic anhydride/acetonitrile solution in the presence of a phosphate buffer having a pH in the range of 7.0 to 9.0 and allowing the conversion of amine and/or hydroxyl moieties of the biogenic amine, precursor, or metabolite thereof to form a propionyl derivative of the biogenic amine; followed by (ii) adding to the reaction mixture obtained in step (i) a carbodiimide compound and an electrophilic amine-containing compound, and allowing the carbodiimide-mediated derivatization of carboxylic acid moieties of the biogenic amine, precursor, or metabolite thereof.

A method for determining in a sample, by mass spectrometry, the amount of one or more analytes selected from the group consisting of N-acetylthreonine, TMAP, phenylacetylglutamine, tryptophan, creatinine, meso-erythritol, arabitol, myo-inositol, N-acetyl serine, N-acetylalanine, 3-methylhistidine, trans-4-hydroxyproline, kynurenine, urea, C-glycosyltryptophan, 3-indoxyl sulfate, pseudouridine, and combinations thereof is described. The method comprises subjecting the sample to an ionization source under conditions suitable to produce one or more ions detectable by mass spectrometry from each of the one or more of the analytes; measuring, by mass spectrometry, the amount of the one or more ions from each of the one or more analytes; and using the measured amount of the one or more ions to determine the amount of each of the one or more analytes in the sample. Also described is a kit comprising one or more isotopically labeled analogues as internal standards for each of the one or more analytes.

The present disclosure provides a method for detecting L-serine based on Escherichia coli cysteine desulfurase, and belongs to the technical field of amino acid detection. The method includes the steps of: reacting an unknown sample containing L-serine with E. coli cysteine desulfurase in vitro to produce a red substance, and qualitatively or quantitatively determining L-serine content in the unknown sample by observing a color of the red substance or determining content thereof. The method provided by the present disclosure is simple and feasible in technical operation, few in reaction steps, and capable of directly qualitatively detecting by naked eyes and quantitatively detecting the L-serine content.

The present invention provides an alternative L-glutamate oxidase that allows for measurement of L-glutamate. More specifically, the present invention provides the following L-glutamate oxidase mutant (a) or (b) and the like: (a) an L-glutamate oxidase mutant including an amino acid sequence that has 90% or more identity to an amino acid sequence of SEQ ID NO: 3 and exhibits an activity of oxidizing L-glutamate, except an L-glutamate oxidase including an amino acid sequence of SEQ ID NO: 1; or (b) an L-glutamate oxidase mutant comprising a peptide linker consisting of 1 to 20 amino acid residues which is inserted into one or more sites selected from the group consisting of (1) a site in a region proximity to a boundary between α1 and α2 regions, (2) a site in a region proximity to a boundary between α2 and γ regions and (3) a site in a region proximity to a boundary between γ and β regions in the L-glutamate oxidase mutant (a), and having the activity of oxidizing L-glutamate.