Prolidase deficiency and the biochemical assays used in its diagnosis

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.

Electrophoretic deposition of Ru(bpy)32+ in vertically-ordered silica nanochannels: A solid-state electrochemiluminescence sensor for prolidase assay

Prolidase (PLD) plays a crucial role as a dipeptidase in various physiological processes, specifically involved in the cleavage of proline-containing dipeptides for efficient recycling of proline. The accurate determination of PLD activity holds significant importance in clinical diagnosis. Herein, a solid-state electrochemiluminescence (ECL) biosensor was developed to address the urgent need for PLD assay. The Ru(bpy)32+ was electrophoretically deposited within the nanochannels of vertically-ordered mesoporous silica film (VMSF) on indium tin oxide (ITO) electrodes. The Ru(bpy)32+-deposited VMSF/ITO (Ru-VMSF/ITO) exhibited a remarkable ECL response towards proline, attributed to the enhanced concentration of the reactants and improved electron transfer resulting from the nanoconfinement effect. As PLD specifically enzymolyzed the Gly-Pro dipeptide to release proline, a proline-mediated biosensor was developed for PLD assay. Increased PLD activity led to enhanced release of proline into the porous solid-state ECL sensors, resulting in a more robust ECL signal. There was a linear relationship between ΔECL intensity and logarithmic concentration of PLD in the range of 10-10000 U/L, with a detection limit of 1.98 U/L. Practical tests demonstrated the reliability and convenience of the proposed bioassay, making it suitable for widespread application in PLD assays.

Comparison of the optimized direct spectrophotometric serum prolidase enzyme activity assay method with the currently used spectrophotometric assay methods and liver fibrosis indexes to distinguish the early stages of liver fibrosis in patients with chronic hepatitis B infection

OBJECTIVE

The aim of this study was to optimize the currently used direct spectrophotometric serum prolidase enzyme activity (SPEA) assay method and compare its diagnostic accuracy with current precipitation and direct spectrophotometric assay methods, AST-to-ALT ratio, age platelet index, AST-to-platelet ratio index, cirrhosis discriminate score, Doha score, FIB-4, FibroQ, fibrosis index, Goteborg University Cirrhosis Index , King's score, and Pohl score for distinguishing Ishak F0 from F1-F3 in patients with chronic hepatitis B (CHB) infection.

METHODS

Liver biopsy results from 112 patients were included in this study.

RESULTS

The SPEA values were 529 (292-794) U/L, 671 (486-927) U/L, and 1077 (867-1399) U/L with the precipitation, current, and optimized direct spectrophotometric assay methods, respectively. According to multivariate logistic regression analysis optimized direct spectrophotometric SPEA was the only statistically significant parameter to predict the early stages of liver fibrosis.

CONCLUSIONS

Optimized direct spectrophotometric SPEA assay method could be used to distinguish early stages of liver fibrosis in patients with CHB infection instead of the currently used spectrophotometric SPEA assay methods and other evaluated liver fibrosis indexes.

Prolidase deficiency: A novel PEPD missense variant in exon 2

Prolidase deficiency is an autosomal recessive disease that causes impaired collagen degradation. Altered collagen homeostasis results in the intracellular accumulation of imidodipeptides, which contain proline and hydroxyproline. The many clinical manifestations of prolidase deficiency include dysmorphic facial features, skeletal deformities, hepatosplenomegaly, necrotizing skin ulcers, and recurrent infections. Current clinical knowledge of this genetic disease relies upon few case reports due to its extreme rarity. Diagnosis is dependent on the detection of a pathologic gene variant. Additional diagnostic confirmation may be provided by urine amino acid quantification or reduced in vitro prolidase activity. We present a case of prolidase deficiency caused by a novel variant manifested by skeletal malformations and lifelong multisystemic infections. Genetic testing revealed a homozygous missense variant in the PEPD gene at nucleotide position 200, whereby adenine was replaced by guanine (c.200A > G). The corresponding amino acid change replaced glutamine with arginine at codon 67 (p.Gln67Arg). After boiling the urine sample for hydrolysis, quantitative urine amino acids demonstrated a markedly elevated proline level, confirming the diagnosis. We also provide a discussion of the pathophysiology, clinical manifestations, diagnostic testing, and clinical management of this disease.

Prolidase activity in aqueous and serum samples of cataract cases with Pseudoexfoliation syndrome

Pseudoexfoliation syndrome (PEX) represents an age-related systemic disease that is characterized by the accumulation of extracellular matrix material in ocular tissues and visceral organs. Abnormal matrix remodeling is thought to be one of the important factors in the etiopathogenesis of the disease. Prolidase represents an enzyme, which takes a significant part in collagen biosynthesis and remodeling of the extracellular matrix. The purpose of the current research was to assess the prolidase enzyme activity in the aqueous and serum samples of subjects with PEX. The study population consisted of 66 subjects, involving 33 subjects with age-related cataract among patients with PEX and 33 subjects with age-related cataract without PEX. The prolidase activity measurement was performed using the modified Chinard's method. Significantly increased aqueous prolidase activity was detected in the group with PEX (p < 0.01). Despite about a three times higher increase in the serum prolidase activity of the group with PEX in comparison with the control group, the two groups did not differ statistically significantly (p > 0.05). The high prolidase enzyme activity in the aqueous samples of subjects with PEX suggests that the collagen cycle and the remodeling of the extracellular matrix are accelerated. These results can be a guide for understanding the formation mechanisms of PEX.

Quantitative analysis of the natural history of prolidase deficiency: description of 17 families and systematic review of published cases

PURPOSE

Prolidase deficiency is a rare inborn error of metabolism causing ulcers and other skin disorders, splenomegaly, developmental delay, and recurrent infections. Most of the literature is constituted of isolated case reports. We aim to provide a quantitative description of the natural history of the condition by describing 19 affected individuals and reviewing the literature.

METHODS

Nineteen patients were phenotyped per local institutional procedures. A systematic review following PRISMA criteria identified 132 articles describing 161 patients. Main outcome analyses were performed for manifestation frequency, diagnostic delay, overall survival, symptom-free survival, and ulcer-free survival.

RESULTS

Our cohort presented a wide variability of severity. Autoimmune disorders were found in 6/19, including Crohn disease, systemic lupus erythematosus, and arthritis. Another immune finding was hemophagocytic lymphohistiocytosis (HLH). Half of published patients were symptomatic by age 4 and had a delayed diagnosis (mean delay 11.6 years). Ulcers were present initially in only 30% of cases, with a median age of onset at 12 years old.

CONCLUSION

Prolidase deficiency has a broad range of manifestations. Symptoms at onset may be nonspecific, likely contributing to the diagnostic delay. Testing for this disorder should be considered in any child with unexplained autoimmunity, lower extremity ulcers, splenomegaly, or HLH.

Serum prolidase level in patients with brucellosis and its possible relationship with pathogenesis of the disease: a prospective observational study

Background/aim

Changes in collagen metabolism and fibroblastic activity may play a role in the pathogenesis of brucellosis. The prolidase enzyme plays an important role in collagen synthesis. We aimed to investigate the association of prolidase levels with brucellosis.

Materials and methods

Serum prolidase levels in 20 patients newly diagnosed with brucellosis were compared with levels in 30 healthy control subjects. Patients with brucellosis were reassessed 3 months later for prolidase, other laboratory measurements, and response to treatment.

Results

The levels of serum prolidase were significantly higher in brucellosis patients compared with those of healthy controls. Prolidase, sedimentation, and C-reactive protein levels were significantly lower after antibrucellosis treatment than before treatment.

Conclusion

The current study is the first to demonstrate significantly increased serum prolidase levels in patients with brucellosis compared with healthy controls. Prolidase levels also significantly decreased with antibrucellosis treatment. This finding provides a new experimental basis to understand the pathogenesis of brucellosis in relation to collagen metabolism. The increase in serum prolidase levels might be related to several factors such as tissue destruction, increased fibroblastic activity, and granuloma formation, all of which are involved in the natural history of brucellosis.

Solitary Mastocytoma of the Eyelid in an Adult Patient With Prolidase Deficiency

Prolidase deficiency and solitary mastocytoma of the eyelid are both exceedingly rare. Prolidase deficiency is an inherited connective tissue disorder that has systemic sequelae, such as intractable skin ulceration, poor wound healing, recurrent infections, and intellectual impairment. Cutaneous mastocytoma is an isolated, aberrant cutaneous aggregation of mast cells. A case of an adult with severe prolidase deficiency who developed cutaneous mastocytoma of the eyelid was presented. To the authors' knowledge, adult-onset solitary mastocytoma of the eyelid has never been reported previously.

Serum prolidase activity and oxidant-antioxidant status in children with chronic hepatitis B virus infection

BACKGROUND

Chronic hepatitis B (CHB) is a global health problem that can result in serious complications associated with collagen degradation. Prolidase is a specific imidodipeptidase that plays an important role in the breakdown of collagen. The aim of this study was to investigate prolidase activity and oxidant-antioxidant status in children with CHB.

METHODS

This prospective case control study includes 38 patients with CHB, 31 patients with inactive hepatitis B (IHB), and 29 healthy matched control subjects. Serum prolidase enzyme activity (SPEA), total antioxidant capacity (TAC), total oxidative activity (TOA), and malondialdehyde (MDA) level were measured and oxidative stress index (OSI) was calculated for each group.

RESULTS

Patients with CHB had significantly higher SPEA levels (207.82 ± 186.80 IU/L) than did the controls (58.6 ± 38.1 IU/L) and IHB patients (67.1 ± 39.9) (p < 0.001). CHB patients also had significantly higher TOA (45.0 ± 19.9 vs. 29.4 ± 11.7 (μmolH2O2 Eq./L), p = 0.005), OSI (33.1 ± 21.4 vs. 17.5 ± 10.2, p = 0.002) and MDA (13.4 ± 4.0 vs. 7.8 ± 2.6 μm/L, p < 0.001) values compared with the controls. TOA (32.0 ± 10.0) and OSI (15.4 ± 11.0) values of IHB patients were significantly lower than those of CHB patients (p < 0.05). SPEA had significant correlations with HBV- DNA and ALT values (r =0.514 and r =0.454, p < 0.001).

CONCLUSION

Our results suggest that prolidase activity can be considered as a reliable marker for CHB and increased oxidative stress appears to be related to chronicity of the disease.

Evaluation of the utility of serum prolidase as a marker for liver fibrosis

BACKGROUND

Liver dysfunction is common and often unrecognized. Liver biopsy is the gold standard in the assessment of liver fibrosis, but has disadvantages. We assessed the diagnostic accuracy of serum prolidase enzyme activity (SPA) in predicting the presence and degree of liver fibrosis, as compared with liver biopsy. Further, we evaluated the effect of hemolysis on measured SPA levels.

METHODS

We undertook a prospective case control study. Thirty eight outpatients without apparent liver illness and 20 patients with liver pathology scheduled to undergo liver biopsy had their SPA levels measured.

RESULTS

Patients undergoing liver biopsy had higher SPA levels (361 (268) IU/l [median (interquartile range)]) compared with controls (169 (160) (P < 0.001)). A SPA cutoff value of 200 IU/l yielded a sensitivity of 89%, specificity of 59%, an odds ratio of 11.5, negative predictive value of 92%, and a positive predictive value of 50%. Hemolysis causes an apparent increase in SPA levels.

CONCLUSION

Higher SPA levels in patients undergoing liver biopsies compared with controls may reflect the presence of liver fibrosis. SPA levels could not be used to stage the degree of fibrosis. SPA measurement may be useful in the diagnostic workup of suspected liver disease.

Prolidase and oxidative stress in chronic hepatitis C

BACKGROUND

Hepatitis C infection represents a common healthcare issue worldwide. The present trial was designed to investigate the role of prolidase, an enzyme that is significantly involved in the biosynthesis of collagen, and of the oxidative stress that is considered to be involved in the pathogenesis of various diseases, in the chronic hepatitis C infection. The trial was performed to assess the serum prolidase enzyme level and the oxidative-antioxidative status and to determine the relation between the serum prolidase activity and the oxidative stress parameters.

METHODS

A total of 95 individuals, including 55 patients with chronic hepatitis C infection (CHC) and 40 healthy adults, were enrolled in the trial. The values for prolidase, the total antioxidant status (TAS), the total oxidative stress (TOS), the oxidative stress index (OSI), sulfhydryl (SH), lipid peroxidation LOOH, catalase (CAT), and ceruloplasmin were measured and compared between the patient groups.

RESULTS

The prolidase, TOS, LOOH, CAT, and the OSI values were higher in the chronic hepatitis C group compared to the control group (P < 0.001). The TAS, SH, and ceruloplasmin levels were lower in the CHC group relative to the control group (P < 0.001).

CONCLUSION

We suppose that the values of prolidase and the oxidative stress are increased while the antioxidant levels are decreased in CHC. As a result, prolidase and the oxidative stress seem to be related with the progression of the disease.

Improved prolidase activity assay allowed enzyme kinetic characterization and faster prolidase deficiency diagnosis

BACKGROUND

Prolidase is a metallo-exopeptidase hydrolyzing X-Pro and X-Hyp dipeptides. Its absence or reduced level is typical in prolidase deficiency (PD) patients, and altered prolidase activity was reported in various diseases. Therefore, standardized and accurate measurement of prolidase activity is essential for PD diagnosis, as well as to elucidate the pathophysiology of other disorders.

METHODS

Human recombinant prolidase was used to optimize a spectrophotometric enzyme activity assay. Kinetic parameters and Mn(2+) affinity were evaluated. The method was validated on blood and fibroblasts from PD patients.

RESULTS

An activation step consisting in prolidase incubation with 1 mmol/l MnCl(2) and 0.75 mmol/l reduced glutathione at 50°C for 20 min was necessary to obtain the maximum activity and to accurately determine, for the recombinant enzyme, V(max) (489 U/mg), K(m) (5.4 mM) and Mn(2+) affinity (54 mM(-1)). The method applied to PD diagnosis revealed an intra-assay CV=8% for blood and 9% for fibroblasts lysates. The inter-assay CV was 21% for blood and 20% for cell lysates.

CONCLUSION

We optimized a faster spectrophotometric method to measure the activity when the enzyme is fully activated, this is crucial to allow a reliable evaluation of prolidase activity from different sources.

Prolidase activity dysregulation and its correlation with oxidative-antioxidative status in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a consequence of an underlying chronic inflammatory disorder of the airways that is usually progressive and causes dysregulation in the metabolism of collagen. Prolidase has an important role in the recycling of proline for collagen synthesis and cell growth.

OBJECTIVE

We measured and compared prolidase activity in healthy individuals with COPD patients to find out that whether its activity might reflect disturbances of collagen metabolism in the patients. We also investigated oxidative-antioxidative status and its relationship with prolidase activity in this disease.

METHODS

Thirty voluntary patients with COPD and 30 healthy control subjects with similar age range and sex were included into the study. Plasma prolidase activities, total antioxidant capacity (TAC) and lipid peroxidation (LPO) levels were measured in the patient and control groups.

RESULTS

Plasma prolidase activity and TAC levels were significantly lower, and LPO levels were significantly higher in the patients than those in the control subjects (P<0.05, P<0.001, and P<0.001, respectively). Significant correlations were detected between plasma prolidase activity and TAC and LPO levels in the patients group (r=0.679, P<0.001; r=-426, P<0.05, respectively).

CONCLUSIONS

The results suggest that oxidative-antioxidative balance and collagen turnover are altered by the development of COPD in human lungs, and prolidase activity may reflect disturbances of collagen metabolism in this pulmonary disease. Monitoring of plasma prolidase activity and oxidative-antioxidative balance may be useful in evaluating fibrotic processes and oxidative damage in the chronic inflammatory lung disease in human.

Serum prolidase activity in idiopathic and ischemic cardiomyopathy patients

Idiopathic and ischemic dilated cardiomyopathies (DCM) are the most common types of DCM, and both exhibit the same histopathological feature of fibrosis. Prolidase is an enzyme that serves a rate-limiting function in collagen turnover. Several studies have shown increased prolidase activity in fibrosis, though controversy persists. In this study, we measured prolidase enzyme activity in patients with idiopathic or ischemic DCM and in healthy controls, making this, to our knowledge, the first study to do so. What we found is that serumprolidase activity was significantly lower in both DCM groups relative to healthy volunteers and lower in ischemic DCM than idiopathic. These intriguing results could be attributed either to decreased collagen turnover in the heart tissues in which DCM develops, a result of diminished functional heart tissue, or to decreased physical activity levels among DCM patients stemming from their heart failure. Either way, further studies are needed to verify and clarify our results.

Prolidase deficiency: it looks like systemic lupus erythematosus but it is not

Three siblings with recalcitrant leg ulceration, splenomegaly, photosensitive rash, and autoantibodies were suspected of having prolidase deficiency. Urine was checked for iminodipeptiduria, fibroblasts were cultured and analyzed for prolidase activity, and DNA was extracted for identifying the causative mutation. Glycyl proline was found as the dominant dipeptide in the urine. The activity of proline dipeptidase in fibroblasts was 2.5% of control fibroblasts. Sequence analysis of the PEPD gene revealed a homozygous nonsense C-->G transition at nucleotide 768. In conclusion, prolidase deficiency was diagnosed in siblings with skin ulceration autoantibodies and a lupus-like disease. A novel nonsense mutation was found, associated with the severe outcome of our patients.

Prolidase activity and oxidative status in patients with thalassemia major

AIM

Prolidase is a specific imidodipeptidase involved in collagen degradation. The increase in the enzyme activity is believed to be correlated with the increased intensity of collagen degradation. The study aimed to evaluate the relationship between prolidase activity and oxidative status in patients with thalassemia major.

METHODS

Comparison was made between 87 patients diagnosed with thalassemia major and 33 healthy children of similar age and gender. Mean age of the subjects was 7.5+/-4.3 years in the group of patients with thalassemia major and 8.9+/-3.1 years in the control group. Serum prolidase activity was measured spectrophotometrically. Oxidative status was determined using total oxidant status (TOS), total antioxidant capacity (TAC), and oxidative stress index (OSI) measurement.

RESULTS

Prolidase activity was significantly increased in patients with thalassemia major (53.7+/-8.7 U/l) compared to the control group (49.2+/-7.2 U/l, P<0.001). TOS was significantly increased in the patient group (5.31+/-3.14 mmol H2O2 equiv./l) compared to the control group (3.49+/-2.98 mumol H2O2 equiv./l) and the OSI was also significantly increased in the patient group (3.86+/-3.28 arbitrary unit) compared to the control group (2.53+/-2.70 arbitrary unit) (P<0.0001 and P<0.001, respectively), while there were no significant differences between the patient (1.61+/-0.30 mumol Trolox equiv./l) and control (1.64+/-0.33 mumol Trolox equiv./l) groups with respect to TAC.

CONCLUSION

Significant increases in prolidase activity in patients with thalassemia major may constitute a key parameter in demonstrating a disorder of the collagen metabolism.

Structural insights into the dual activities of the nerve agent degrading organophosphate anhydrolase/prolidase

The organophosphate acid anhydrolase (OPAA) is a member of a class of bimetalloenzymes that hydrolyze a variety of toxic acetylcholinesterase-inhibiting organophosphorus compounds, including fluorine-containing chemical nerve agents. It also belongs to a family of prolidases, with significant activity against various Xaa-Pro dipeptides. Here we report the X-ray structure determination of the native OPAA (58 kDa mass) from Alteromonas sp. strain JD6.5 and its cocrystal with the inhibitor mipafox [N,N'-diisopropyldiamidofluorophosphate (DDFP)], a close analogue of the nerve agent organophosphate substrate diisopropyl fluorophosphate (DFP). The OPAA structure is composed of two domains, amino and carboxy domains, with the latter exhibiting a "pita bread" architecture and harboring the active site with the binuclear Mn(2+) ions. The native OPAA structure revealed unexpectedly the presence of a well-defined nonproteinaceous density in the active site whose identity could not be definitively established but is suggestive of a bound glycolate, which is isosteric with a glycine (Xaa) product. All three glycolate oxygens coordinate the two Mn(2+) atoms. DDFP or more likely its hydrolysis product, N,N'-diisopropyldiamidophosphate (DDP), is present in the cocrystal structure and bound by coordinating the binuclear metals and forming hydrogen bonds and nonpolar interactions with active site residues. An unusual common feature of the binding of the two ligands is the involvement of only one oxygen atom of the glycolate carboxylate and the product DDP tetrahedral phosphate in bridging the two Mn(2+) ions. Both structures provide new understanding of ligand recognition and the prolidase and organophosphorus hydrolase catalytic activities of OPAA.

Diagnostic value of serum prolidase enzyme activity to predict the liver histological lesions in non-alcoholic fatty liver disease: a surrogate marker to distinguish steatohepatitis from simple steatosis

Determination of the liver histological lesions with noninvasive tests is an important part of the diagnostic work-up of patients with non-alcoholic fatty liver disease (NAFLD). We aimed to determine the predictive value of noninvasive biochemical markers, serum prolidase enzyme activity (SPEA), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and AST/ALT ratio for the liver histological lesions. Fifty-four liver biopsy-proven patients with NAFLD and 37 healthy controls were enrolled to the study. The diagnostic accuracies of biochemical markers were evaluated by receiver operating characteristic (ROC) curves and multiple linear regression analysis to predict the degree of fatty infiltration, lobular inflammation, NAFLD activity score, and stage of fibrosis. The SPEA of patients with steatohepatitis is significantly increased compared with the patients with simple steatosis and controls (1,338 [1,138-1,624] U/l; 974 [768-1,160] U/l; 972 [862-1,122] U/l, shown as median [25th-75th interquartile range], respectively, P < 0.0001). SPEA was positively correlated with the grade of liver fatty infiltration, lobular inflammation and NAFLD activity score, and stage of fibrosis, (r = 0.377, P < 0.005; r = 0.443, P < 0.001; r = 0.457, P < 0.001; r = 0.321, P < 0.018, respectively). SPEA was the best predictor for distinguishing steatohepatitis from simple steatosis according to the ROC analysis (area under the curve [AUC]: 0.85). Multivariate analysis revealed that the most useful single test for predicting lobular inflammation, NAFLD activity score, and fibrosis was SPEA, and for predicting the fatty infiltration, it was ALT (P < 0.00001, P < 0.001, P < 0.0001, P < 0.0001, respectively). This study demonstrated that SPEA can accurately predict the degree and stage of all histological lesions in NAFLD. It could be helpful for distinguishing steatohepatitis from simple steatosis and reducing the need for liver biopsy in the majority of patients with NAFLD.

Proteomics of canine lymphoma identifies potential cancer-specific protein markers

PURPOSE

Early diagnosis of cancer is crucial for the success of treatment of the disease, and there is a need for markers whose differential expression between disease and normal tissue could be used as a diagnostic tool. Spontaneously occurring malignancies in pets provide a logical tool for translational research for human oncology. Lymphoma, one of the most common neoplasms in dogs, is similar to human non-Hodgkin's lymphoma and could serve as an experimental model system.

EXPERIMENTAL DESIGN

Thirteen lymph nodes from normal dogs and 11 lymph nodes from dogs with B-cell lymphoma were subjected to proteomic analysis using two-dimensional PAGE separation and matrix-assisted laser desorption/ionization time-of-flight analysis.

RESULTS

A total of 93 differentially expressed spots was subjected to matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry analysis, and several proteins that showed differential expression were identified. Of these, prolidase (proline dipeptidase), triosephosphate isomerase, and glutathione S-transferase were down-regulated in lymphoma samples, whereas macrophage capping protein was up-regulated in the lymphoma samples.

CONCLUSIONS

These proteins represent potential markers for the diagnosis of lymphoma and should be further investigated in human samples for validation of their utility as diagnostic markers.

Molecular characterisation of six patients with prolidase deficiency: identification of the first small duplication in the prolidase gene and of a mutation generating symptomatic and asymptomatic outcomes within the same family

Prolidase deficiency (PD) is a rare autosomal recessive connective tissue disorder caused by mutations in the prolidase gene. The PD patients show a wide range of clinical outcomes characterised mainly by intractable skin ulcers, mental retardation and recurrent respiratory infections. Here we describe five different PEPD mutations in six European patients. We identified two new PEPD mutant alleles: a 13 bp duplication in exon 8, which is the first reported duplication in the prolidase gene and a point mutation resulting in a change in amino acid E412, a highly conserved residue among different species. The E412K substitution is responsible for the first reported phenotypic variability within a family with severe and asymptomatic outcomes.