Separation and Quantitation of Peptides and Amino Acids in Normal Human Urine

Lou, Marjorie F.; Hamilton, Paul B.

doi:10.1002/9780470110454.ch3

Cited by 10 publications

(1 citation statement)

References 161 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Analyses of amino acids released by hydrolysis therefore suggest that the biuret method substantially overestimates urinary peptide excretion. Analyses of peptide components in urine have shown a substantial diversity of dipeptides and other small peptides, but the total quantity of small peptide components has appeared to be small relative to the content of free amino acids (28,29 ).…”

mentioning

confidence: 99%

Cross-Reactivity of Amino Acids and Other Compounds in the Biuret Reaction: Interference with Urinary Peptide Measurements

Hortin¹,

Meilinger²

2005

Clinical Chemistry

View full text Add to dashboard Cite

Background: Biuret assays for total protein measurement are considered to react with all peptides longer than 2 residues. Some studies using biuret assays of urine suggest that small peptides generally are more abundant than proteins in urine, but it is not clear whether this is a problem of assay specificity. Methods: We analyzed the specificity and kinetics of a biuret reaction for solutions of amino acids, organic compounds, peptides, proteins, and ultrafiltered urine specimens and compared the results with standard clinical assays for protein measurement. Results: The biuret assay cross-reacted with several amino acids, dipeptides, and other organic compounds able to form 5-or 6-member ring chelation complexes with copper. Reactions with amino acids and dipeptides had higher absorbance maxima (blue color) than with larger peptides and proteins (purple). Compounds forming potential 4-, 7-, 8-, or 9-member ring complexes with copper had low reactivity. Amino acid amides, dipeptides, and longer peptides had substantial reactivity, except those containing proline. Proteins and polypeptides had similar biuret reactivities per peptide bond, but reaction kinetics were slower for proteins than peptides. Urine specimens ultrafiltered through 3-kDacutoff membranes had substantial biuret reactivity, but absorbance maxima were consistent with cross-reactive amino acids rather than peptides. Conclusions: Many compounds, including amino acids, amino acid derivatives, and dipeptides, cross-react in biuret assays. Our studies improve understanding of the specificity of endpoint and kinetic biuret assays widely used in clinical laboratories. Amino acids, urea, and

show abstract

mentioning

confidence: 99%

Cross-Reactivity of Amino Acids and Other Compounds in the Biuret Reaction: Interference with Urinary Peptide Measurements

Hortin¹,

Meilinger²

2005

Clinical Chemistry

View full text Add to dashboard Cite

show abstract

Spurious Elevation of Multiple Urine Amino Acids by Ion-Exchange Chromatography in Patients with Prolidase Deficiency

Ferreira

Cusmano‐Ozog

2016

JIMD Reports

View full text Add to dashboard Cite

The enzyme prolidase cleaves dipeptides where the C-terminal amino acid corresponds to proline or hydroxyproline. As a consequence, a deficiency of this enzyme leads to accumulation of these dipeptides, which correspondingly are found to be elevated in urine. In fact, the absence of dipeptiduria is sufficient to rule out a diagnosis of prolidase deficiency. However, given the fact that these dipeptides elute at the same position as more common amino acids, the analyzer's software will instead call an elevation of these corresponding amino acids. Thus, an elevation of glycylproline, aspartylproline, glutamylproline, threonylproline and serylproline, valylproline, leucylproline, isoleucylproline, alanylproline, phenylalanylproline, and lysylproline will instead be interpreted as an elevation of leucine, citrulline, methionine, isoleucine, beta-aminoisobutyric acid, gamma-aminobutyric acid, ethanolamine, tyrosine, histidine, and anserine/carnosine, respectively. This particular profile of elevated amino acids, however, can easily be overlooked. We hope that the recognition of this characteristic pattern of falsely elevated urinary amino acids will aid in the recognition of prolidase deficiency.

show abstract

Quantitation of methylated basic amino acids in biological fluid

Lou

Siena

1981

Biochemical Medicine

View full text Add to dashboard Cite

Separation and Quantitation of Peptides and Amino Acids in Normal Human Urine

Cited by 10 publications

References 161 publications

Cross-Reactivity of Amino Acids and Other Compounds in the Biuret Reaction: Interference with Urinary Peptide Measurements

Cross-Reactivity of Amino Acids and Other Compounds in the Biuret Reaction: Interference with Urinary Peptide Measurements

Spurious Elevation of Multiple Urine Amino Acids by Ion-Exchange Chromatography in Patients with Prolidase Deficiency

Quantitation of methylated basic amino acids in biological fluid

Contact Info

Product

Resources

About