A fluorometric method for dipeptidase activity measurement in urine, using L-alanyl-L-alanine as substrate.
A new method for the measurement of urinary dipeptidase activity is described. The action of dipeptidase on L-Ala-L-Ala results in production of an L-alanine, and this amino acid is simultaneously determined by an L-alanine dehydrogenase-diaphorase system. As urinary substances do not affect this reaction, the measurement can be accomplished without prior dialysis. The mean value +/- S.D. for normals was found to be 12.0 +/- 4.4 IU/g of creatinine. Elevated values were found in chronic nephritis (55.9 +/- 35.0 IU/g of creatinine, P less than 0.001 vs. normal), acute nephritis (46.6 +/- 29.9 IU/g of creatinine, P less than 0.001), and nephrotic syndrome (43.3 +/- 36.5 IU/g of creatinine, P less than 0.001). The dipeptidase activity thus measured showed a significant correlation with dipeptidase activity against L-Leu-L-Leu as substrate. On disc polyacrylamide gel electrophoresis, the urinary dipeptidase of a patient with chronic nephritis appeared as one band with similar mobility to human kidney dipeptidase F. Urinary dipeptidase in a patient with chronic nephritis was identical to human kidney dipeptidase on double immunodiffusion analysis.
D050788:Alanine Dehydrogenase; D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism; D004150:Dipeptidases / Q000652:urine*; D004151:Dipeptides / Q000378:metabolism*; D004589:Electrophoresis, Disc; D006801:Humans; D005779:Immunodiffusion / Q000379:methods; D007668:Kidney / Q000201:enzymology; D007674:Kidney Diseases / Q000201:enzymology; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity
D004151:Dipeptides; C002956:alanylalanine; C038361:leucylleucine; D000594:Amino Acid Oxidoreductases; D050788:Alanine Dehydrogenase; D008058:Dihydrolipoamide Dehydrogenase; D004150:Dipeptidases