Optimization of a capillary electrophoretic method to detect and quantify the Gly-Pro dipeptide in complex matrices from long term cultured prolidase deficiency fibroblasts

Prolidase activity assays. A survey of the reported literature methodologies

Prolidase (EC.3.4.13.9) is a dipeptidase known nowadays to play a pivotal role in several physiological and pathological processes. More in particular, this enzyme is involved in the cleavage of proline- and hydroxyproline-containing dipeptides (imidodipeptides), thus finely regulating the homeostasis of free proline and hydroxyproline. Abnormally high or low levels of prolidase have been found in numerous acute and chronic syndromes affecting humans (chronic liver fibrosis, viral and acute hepatitis, cancer, neurological disorders, inflammation, skin diseases, intellectual disability, respiratory infection, and others) for which the content of proline is well recognized as a clinical marker. As a consequence, the accurate analytical determination of prolidase activity is of greatly significant importance in clinical diagnosis and therapy. Apart from the Chinard's assay, some other more sensitive and well validated methodologies have been published. These include colorimetric and spectrophotometric determinations of free proline produced by enzymatic reactions, capillary electrophoresis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, electrochemoluminescence, thin layer chromatography, and HPLC. The aim of this comprehensive review is to make a detailed survey of the in so far reported analytical techniques, highlighting their general features, as well as their advantages and possible drawbacks, providing in the meantime suggestions to stimulate further research in this intriguing field.

Recent developments in capillary electrophoresis and capillary electrochromatography of peptides

The article gives a comprehensive review on the recent developments in the applications of high-performance capillary electromigration methods, zone electrophoresis, isotachophoresis, isoelectric focusing, affinity electrophoresis, electrokinetic chromatography, and electrochromatography, to analysis, preparation, and physicochemical characterization of peptides. The article presents new approaches to the theoretical description and experimental verification of electromigration behavior of peptides, covers the methodological aspects of capillary electroseparations of peptides, such as rational selection of separation conditions, sample preparation, suppression of peptide adsorption, new developments in individual separation modes, and new designs of detection systems. Several types of applications of capillary electromigration methods to peptide analysis are presented: conventional qualitative and quantitative analysis, purity control, determination in biomatrices, monitoring of chemical and enzymatical reactions and physical changes, amino acid and sequence analysis, and peptide mapping of proteins. Some examples of micropreparative peptide separations are given and capabilities of capillary electromigration techniques to provide important physicochemical characteristics of peptides are demonstrated.

The role of emerging techniques in the investigation of prolidase deficiency: From diagnosis to the development of a possible therapeutical approach

The aim of the present article is to review the efforts performed in the past two decades by numerous research groups for the development of methods that allow a correct diagnosis of prolidase deficiency (PD), a rare autosomal recessive disorder and for the rationalization of a possible therapeutic intervention on these patients. In particular, the interest of the reader is focused on the application of capillary electrophoresis (i) for the detection of biological markers that reflect the pathological feature of the disease and (ii) for the determination of the efficiency of a carrier system in delivering prolidase inside cells in a possible therapy based on enzyme replacement.

Characterization of a new PEPD allele causing prolidase deficiency in two unrelated patients: natural-occurrent mutations as a tool to investigate structure-function relationship

Prolidase deficiency (PD) is a rare autosomal recessive disorder characterized mainly by skin lesions of the legs and feet, mental retardation, and respiratory infections. Mutations at the PEPD locus, located on chromosome 19, are responsible for this disease. We identified a new PEPD allele in two unrelated Portuguese PD patients by analyses of reverse transcribed PCR-amplified cDNA. We used SSCP analysis of seven overlapping fragments spanning the entire coding region of the gene and detected abnormal SSCP bands in two of them: PD3 (nt 425-743) and PD4 (nt 661-973). Direct sequencing of the mutant cDNA and genomic DNA revealed a new homozygous 3-bp deletion (Y231del) in both cases. Transient expression in PD fibroblasts of wild-type and mutant prolidase cDNA confirmed reduced activity of the construct carrying the 3-bp deletion. The mutation results in a loss of prolidase activity in skin fibroblasts. Intracellular accumulation of Gly-Pro dipeptide in long-term cultured fibroblasts was detected by capillary electrophoresis. The mutation falls in the alpha2 domain of the "pita bread" structure proposed for E. coli and human prolidase by Bazan et al. on the bases of their sequence homology with E. coli methionine aminopeptidase. Taking into account the effects of the described mutations on stability and activity of the enzyme, we propose the identification of three different functional regions.

Determination of prolidase activity using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Proline-containing peptides of the X-proline type are cleaved by the dipeptidase prolidase. The classical method of prolidase assay relied on the colorimetric estimation of the liberated proline with ninhydrin using acidic media and heat. This method, however, gave inconsistent results due to the nonspecificity of the ninhydrin color reaction. We report here a method for the detection of the liberated proline using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Human sera were incubated with a mixture containing the dipeptide glycyl-proline in Tris-HCl supplemented with manganese at 37 degrees C for 24h. The samples were precipitated with trifluoroacetic acid and centrifuged. An aliquot of the supernatant was mixed with an equal volume of ferulic acid solution. An aliquot from this mixture was spotted on a stainless steel mass spectrometry grid and analyzed using MALDI-TOF mass spectrometry. The activity of the enzyme was determined by the complete disappearance of the glycyl-proline peak with the concomitant appearance of the proline peak and can be expressed in terms of the ratio of the area beneath the proline to the area beneath the glycyl-proline peak. Subjects homozygous for prolidase deficiency had a ratio ranging from 0.006 to 0.04 while obligatory heterozygotes had a ratio ranging from around 1.1 to 2.4. Normal subjects had ratios ranging from 9 to 239. Using this method we have unambiguously identified subjects with homozygous or heterozygous prolidase deficiency. In addition to the advantage of rapid sample preparation time, this method is highly specific, reproducible, and sensitive.