Prolidase deficiency: its dermatological manifestations and some additional biochemical studies

Osteoarticular Manifestations of Prolidase Deficiency and Disability: Case Reports of Two Moroccan Sisters

Prolidase deficiency (PD) is a rare autosomal recessive disorder that has symptoms such as chronic skin ulcers, dysmorphic facies, cognitive retardation, hematological anomalies, splenomegaly, and chronic infections. Bone and joint abnormalities were referred occasionally and included the signs and symptoms of prolidase deficiency, but were not deeply investigated in PD patients. We report a case of two PD Moroccan sisters with osteoarticular deformities, some of them were never described before: toes deformities and equinovalgus with fusion and dislocation of a tarsal bone in radiography x-rays.

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.

Clinical Genetics of Prolidase Deficiency: An Updated Review

Prolidase is a ubiquitous enzyme that plays a major role in the metabolism of proline-rich proteins. Prolidase deficiency is a rare autosomal recessive inborn metabolic and multisystemic disease, characterized by a protean association of symptoms, namely intellectual disability, recurrent infections, splenomegaly, skin lesions, auto-immune disorders and cytopenia. To our knowledge, no published review has assembled the different clinical data and research studies over prolidase deficiency. The aim of this study is to summarize the actual state of the art from the descriptions of all the patients with a molecular diagnosis of prolidase deficiency reported to date regarding the clinical, biological, histopathological features, therapeutic options and functional studies.

Prolidase Deficiency in a Mexican-American Patient Identified by Array CGH Reveals a Novel and the Largest PEPD Gene Deletion

Prolidase deficiency (PD) is a rare genetic disorder caused by mutations in the peptidase D (PEPD) gene, affecting collagen degradation. Features include lower extremity ulcers, facial dysmorphism, frequent respiratory infections, and intellectual disability, though there is significant intra- and interfamilial variability. Twenty-eight mutations have been previously reported, all either small deletions/duplications or point mutations discovered by enzyme or DNA assays. PD has been reported in patients of various ethnic backgrounds, but never in the Mexican-American population. We describe the first Mexican-American patient with PD, who presented with typical facial features, developmental delay, microcephaly, and xerosis. Chromosome microarray analysis (CMA) revealed a homozygous deletion in the region of 19q13.11, estimated to be between 124.79 and 195.72 kb in size, representing the largest PEPD gene deletion reported to date and the first discovered by CMA.

Serum prolidase activity in ankylosing spondylitis and rheumatoid arthritis

The aim of the present study was to emphasize the collagen turnover in 2 of the most common chronic inflammatory rheumatic diseases by evaluating serum prolidase activity (SPA) in ankylosing spondylitis (AS) and rheumatoid arthritis (RA). 30 patients who met the modified New York Criteria for the classification of AS, 29 patients who met the 2010 Rheumatoid Arthritis Classification Criteria for the classification of RA, and 31 healthy controls were enrolled in the study. Serum samples of the patients and the controls were collected and SPA was measured by a spectrophotometric method. The comparison of the SPA in these 3 groups was statistically examined. In both patient groups, the SPA was lower than in the control group. SPA in patients with AS was statistically significantly lower than in the control and RA groups (P < 0.001/P = 0.002). No statistically significant difference was found between the RA and the control groups (P = 0.891). In conclusion, lower SPA is presumably associated with decreased collagen turnover and fibrosis, leading to decreased physical functions in both chronic inflammatory musculoskeletal diseases.

Prolidase directly binds and activates epidermal growth factor receptor and stimulates downstream signaling

Prolidase, also known as Xaa-Pro dipeptidase or peptidase D (PEPD), is a ubiquitously expressed cytosolic enzyme that hydrolyzes dipeptides with proline or hydroxyproline at the carboxyl terminus. In this article, however, we demonstrate that PEPD directly binds to and activates epidermal growth factor receptor (EGFR), leading to stimulation of signaling proteins downstream of EGFR, and that such activity is neither cell-specific nor dependent on the enzymatic activity of PEPD. In line with the pro-survival and pro-proliferation activities of EGFR, PEPD stimulates DNA synthesis. We further show that PEPD activates EGFR only when it is present in the extracellular space, but that PEPD is released from injured cells and tissues and that such release appears to result in EGFR activation. PEPD differs from all known EGFR ligands in that it does not possess an epidermal growth factor (EGF) motif and is not synthesized as a transmembrane precursor, but PEPD binding to EGFR can be blocked by EGF. In conclusion, PEPD is a ligand of EGFR and presents a novel mechanism of EGFR activation.

Different effects of sulfur amino acids on prolidase and prolinase activity in normal and prolidase-deficient human erythrocytes

BACKGROUND

Prolidase and prolinase activity is known to be enhanced significantly in some diseases. Recently, the effect of amino acids on prolidase and prolinase activity in normal and prolidase-deficient human erythrocytes was investigated. It was reported that both enzymes were enhanced by glycine and alanine in the presence of MnCl(2).

METHODS

Erythrocytes were isolated from heparinized blood from normal human and a patient with prolidase deficiency. Effects of various sulfur amino acids on prolidase and prolinase activities against iminodipeptides in the presence of 1 or 0.1 mmol/l MnCl(2) were investigated.

RESULTS

Prolinase activity against prolylglycine in normal and prolidase-deficient erythrocyte lysates was inhibited by L-methionine, NAc-L-methionine and D,L-methionine in a concentration-dependent manner, but D-methionine enhanced the activity in low concentrations (0-20 mmol/l). D,L-Homocysteine inhibited the activity more strongly than other sulfur amino acids tested in a concentration-dependent manner. On the other hand, prolidase activity against glycylproline was enhanced by L-methionine, D-methionine, D,L-methionine, D,L-homocysteine thiolactone and D,L-ethionine. The rates of enhancement by these sulfur amino acids were in the following order: D,L-ethionine>D,L-methionine, D-methionine, D,L-homocysteine thiolactone>L-methionine (10 mmol/l).

CONCLUSION

The prolinase activity in normal and prolidase-deficient erythrocyte lysates was inhibited by L-methionine, D,L-ethionine and D,L-homocysteine. On the other hand, prolidase activity in their erythrocyte lysates was enhanced by D,L-ethionine, D-methionine and L-methionine. These results indicate the effects of these sulfur amino acids on prolidase and prolinase activities were different.

Characteristics of Prolidase from the Erythrocytes of Normal Humans and Patients with Prolidase Deficiency and Their Mother

Prolidases I and II were highly purified from human erythrocytes. The effects of various amino acids, MnCl2 and mercaptoethanol, on these two enzymes were investigated. Normal prolidase II was very labile in the absence of MnCl2 or mercaptoethanol. The activity of prolidase II was maintained at about 76% by pre-incubation with MnCl2; it was then activated up to 140% by treatment with mercaptoethanol for 60 minutes at 37 degrees C. Normal prolidases I and II showed the highest activity against glycylproline or methionylproline in the presence of MnCl2. The activity of prolidase I against glycylproline was enhanced strongly by glycine and MnCl2, but not activated in the absence of MnCl2. The activity of prolidase II against methionylproline was enhanced three-fold in the presence of glycine and MnCl2, but its activity against glycylproline was very low even in the presence of MnCl2. A stronger enhancement of this activity was found in normal erythrocytes, and a lower level of this activity was found in erythrocytes of patients treated with glycine, MnCl2 and mercaptoethanol compared to those treated with glycine and MnCl2. The activity of prolidase II against methionylproline in all erythrocytes, of normal humans and of patients, was strongly activated by the addition of glycine with MnCl2 but suppressed by the addition of mercaptoethanol.

Therapeutic apheresis exchange in two patients with prolidase deficiency

BACKGROUND

Prolidase deficiency is a rare genetic disorder for which a cure has not yet been found.

OBJECTIVES

To assess the effectiveness of apheresis exchange as a new therapeutic approach.

METHODS

Apheresis exchanges were repeated monthly for four consecutive months, in parallel, on two patients, replacing prolidase-deficient red blood cells with normal filtered cells. Prolidase activity and urinary dipeptides were determined at regular intervals.

RESULTS

The constant presence of active prolidase inside cells allowed a continuous, although partial, degradation of imidodipeptides, with a concomitant improvement of skin ulceration.

CONCLUSIONS

Apheresis exchange could be a reasonable way of obtaining a clinical improvement in these patients.

Corticosteroid treatment of prolidase deficiency skin lesions by inhibiting iminodipeptide-primed neutrophil superoxide generation

We studied the pathogenetic role of iminodipeptides, and the effects of corticosteroids on the skin lesions of two adult female siblings with prolidase deficiency. The elder sister had had severe skin ulcers and mental retardation since childhood, while the younger sister had shown milder clinical manifestations since late adolescence. The ulcers showed vascular wall thickening and neutrophil infiltration. Oral prednisolone at moderate doses was not effective, but corticosteroid pulse therapy followed by a moderate dose of prednisolone improved the preulcerative indurated lesions and ulcers. A 2-year follow-up of the younger patient indicated that N-formyl methionyl leucyl phenylalanine-induced neutrophil superoxide generation was elevated, in parallel with an increase in the serum iminodipeptide level, when the skin ulcers and preulcerative indurated lesions were most active. Corticosteroid pulse therapy downregulated the superoxide generation by neutrophils. The serum iminodipeptide level, however, did not decrease during 25 days after pulse therapy. These findings suggest that iminodipeptides may play an important part in aggravating the skin lesions by priming neutrophil superoxide generation, and that high-dose corticosteroids improve the skin lesions, probably by inhibiting the infiltration, and superoxide generation by, neutrophils. Neutrophil superoxide generation was more prominent in the elder sister, suggesting that clinical severity may depend on the response of neutrophils to the iminodipeptides. Chronic stimulation by superoxide may cause thickening of cerebral blood vessels and eventual mental retardation.

Amelioration of prolidase deficiency in fibroblasts using adenovirus mediated gene transfer

Prolidase deficiency is an autosomal recessive inherited disease characterized clinically by frequent infections, mental retardation, and various skin lesions. Fundamental treatments for these manifestations have not been established. We performed adenovirus-mediated gene transfer of human prolidase cDNA into fibroblasts from patients with prolidase deficiency. Infection with the adenovirus vector carrying human prolidase cDNA increased prolidase activity in fibroblasts up to approximately 7.5 times of that of normal control fibroblasts. This indicates the feasibility of adenovirus-mediated gene therapy to treat patients with prolidase deficiency in the future.

Localization of prolidase gene expression in scar tissue using in situ hybridization

We investigated prolidase gene expression in human skin by means of Northern blot analysis and in situ hybridization. Northern blot analysis revealed that an mRNA species that was specific for prolidase was present in cultured human skin fibroblasts and keratinocytes. In situ hybridization using non-isotopic riboprobes labeled with digoxigenin and an isotopic riboprobe labeled with [35S]UTP localized prolidase gene expression to fibroblasts and endothelial cells of small vessels in scar tissue. Prolidase mRNA was also prominently expressed in keratinocytes near the basal layer overlying scar tissue. These findings indicate that prolidase may have an important role in wound healing.

Topical treatment of skin ulcers in prolidase deficiency

Prolidase deficiency is a hereditary enzyme deficiency characterized dermatologically by chronic recurrent ulcers and scarring due to increased skin fragility. It has been speculated that the enzyme deficiency causes a relative deficiency of proline in the wounds of these patients and negatively affects clinical healing. Two ulcers in a 17-year-old girl with established prolidase deficiency were treated for 12 weeks with ointments containing amino acids in an open study comparing the effects of 5% proline and a combination of 5% proline plus 5% glycine. Both ointments caused significant reduction of the ulcer size (p < 0.02), but the 5% proline-5% glycine mixture caused a more rapid reduction (0.01 < p < 0.02). The results confirm previous findings in this rare inborn error of metabolism.

The use of liquid chromatography-mass spectrometry for the identification and quantification of urinary iminodipeptides in prolidase deficiency

It has been reported that the urine of patients with prolidase deficiency contains various iminodipeptides with a carboxyl-terminal proline (hydroxyproline). These iminodipeptides have hitherto been detected indirectly by acid hydrolysis or enzymatic digestion, followed by amino acid analysis. In the present study, it was shown that X-Pro could be distinguished from Pro-X when the iminodipeptides were analysed directly by liquid chromatography coupled with atmospheric pressure ionization mass spectrometry (LC/API-MS), with scanning of the protonated molecule ions ([M+H]+). The same procedure also successfully quantified urinary iminodipeptides from patients with prolidase deficiency. A quantitative investigation of two siblings with prolidase deficiency revealed that the patient with severe clinical symptoms excreted more iminodipeptides than the other who did not have serious symptoms. LC/API-MS also revealed iminodipeptides (Gly-Hyp and Pro-Hyp) in the urine of the mother of the patients and in normal volunteers. Patients excreted much more Pro-Hyp than normal volunteers, whereas no quantitative differences were found between the mother and controls. In patients, the excretion of large quantities of X-Pro is due to their very low prolidase activity towards this type of substrate. In the erythrocytes of patients, prolidase activity towards X-Hyp was extremely low; even in the mother and normal volunteers, it was remarkably low in comparison with the activity against X-Pro.

Molecular defect in siblings with prolidase deficiency and absence or presence of clinical symptoms. A 0.8-kb deletion with breakpoints at the short, direct repeat in the PEPD gene and synthesis of abnormal messenger RNA and inactive polypeptide

Prolidase deficiency is an autosomal recessive disorder with highly variable symptoms, including mental retardation, skin lesions, and abnormalities of collagenous tissues. In Japanese female siblings with polypeptide negative prolidase deficiency, and with different degrees of severity of skin lesions, we noted an abnormal mRNA with skipping of 192 bp sequence corresponding to exon 14 in lymphoblastoid cells taken from these patients. Transfection and expression analyses using the mutant prolidase cDNA revealed that a mutant protein translated from the abnormal mRNA had an Mr of 49,000 and was enzymatically inactive. A 774-bp deletion, including exon 14 was noted in the prolidase gene. The deletion had termini within short, direct repeats ranging in size of 7 bp (CCACCCT). The "slipped mispairing" mechanism may predominate in the generation of the deletion at this locus. This mutation caused a 192-bp in-frame deletion of prolidase mRNA and was inherited from the consanguineous parents. The same mutation caused a different degree of clinical phenotype of prolidase deficiency in this family, therefore factor(s) not related to the PEPD gene product also contribute to development of the clinical symptoms. Identification of mutations in the PEPD gene from subjects with prolidase deficiency provides further insight into the physiological role and structure-function relationship of this biologically important enzyme.

Characterization of fibroblast-derived prolidase. The presence of two forms of prolidase

Crude enzyme solutions of prolidase were extracted from cultured human skin fibroblasts derived from control and prolidase-deficient sisters. Two forms of prolidases (prolidase-I and II) were partially purified by high performance liquid chromatography equipped with an ion exchange column. On gel filtration, the relative molecular weights of prolidase-I and II were estimated to be MW = 105,000 and 151,000, respectively. The substrate specificity of partially purified prolidase-I and II in control fibroblasts was estimated against Gly-Pro, Ala-Pro, Met-Pro. Each form of prolidase differed in its substrate specificity. In prolidase-deficient sisters, the elder with typical clinical manifestations and the younger with only slight clinical manifestations, the activity of prolidase-I was absent. However, the activity of prolidase-II was sufficiently present in both sisters. The substrate specificity of prolidase-II in the patients was similar to that of control. No difference in substrate specificity was found between these two patients.

Biochemical basis of prolidase deficiency. Polypeptide and RNA phenotypes and the relation to clinical phenotypes

Cultured skin fibroblasts or lymphoblastoid cells from eight patients with clinical symptoms of prolidase deficiency were analyzed in terms of enzyme activity, presence of material crossreacting with specific antibodies, biosynthesis of the polypeptide, and mRNA corresponding to the enzyme. There are at least two enzymes that hydrolyze imidodipeptides in these cells and these two enzymes could be separated by an immunochemical procedure. The specific assay for prolidase showed that the enzyme activity was virtually absent in six cell strains and was markedly reduced in two (less than 3% of controls). The activities of the labile enzyme that did not immunoprecipitate with the anti-prolidase antibody were decreased in the cells (30-60% of controls). Cell strains with residual activities of prolidase had immunological polypeptides crossreacting with a Mr 56,000, similar to findings in the normal enzyme. The polypeptide biosynthesis in these cells and the controls was similar. Northern blot analyses revealed the presence of mRNA in the polypeptide-positive cells, yet it was absent in the polypeptide-negative cells. The substrate specificities analyzed in the partially purified enzymes from the polypeptide-positive cell strains differed, presumably due to different mutations. Thus, there seems to be a molecular heterogeneity in prolidase deficiency. There was no apparent relation between the clinical symptoms and the biochemical phenotypes, except that mental retardation was present in the polypeptide-negative patients. The activities of the labile enzyme may not be a major factor in modifying the clinical symptoms.

Determination of prolinase activity in plasma. Application to liver disease and its relation with prolidase activity

We describe prolinase (EC 3.4.13.8) activity in human plasma for the first time. Optimum activity was obtained with prolylvaline as substrate and 0.02 mmol/L manganese concentration at pH 9.0. Moreover, preincubation with manganese was not required, contrary to prolidase (EC 3.4.13.9) activity. The mean value observed in 106 subjects without liver and renal disorders was 16 U/L +/- 14 (2 SD). We determined this plasma enzyme activity in patients with acute hepatitis and chronic liver disease. Plasma prolinase activity was strongly dependent upon cytolysis because of the high activity in liver and the low activity in plasma. Of 24 patients with chronic liver disease (4 chronic hepatitis and 20 cirrhosis) and without cytolysis, prolinase activity was slightly increased in only three patients, whereas prolidase activity was increased in 13. This could be due to a difference in the activation of these two enzymes in liver during the fibrotic process.

An autopsy case of prolidase deficiency

A 25-year-old female who suffered from longstanding incurable leg ulcers was found to have prolidase deficiency with iminodipeptiduria. On ultrastructural studies of autopsy specimens, the lamina densa of the epidermal basement membrane was found to show irregular splitting and the basement membranes of the dermal blood vessels were lamellated with interruptions. Lamellar changes and splitting of the basement membranes of the renal tubules, interstitial blood vessels and glomerular capillaries also occurred. These morphological abnormalities seem to be one of causes of the clinical symptomatology.

Studies of rat brain metabolism using proton nuclear magnetic resonance: spectral assignments and monitoring of prolidase, acetylcholinesterase, and glutaminase

The first application of inversion-recovery spin-echo proton nuclear magnetic resonance spectroscopy to the monitoring of reactions in rat brain preparations is presented. The initial report of the assignment of proton spin-echo nuclear magnetic resonance spectra from rabbit brain homogenates (C. R. Middlehurst et al., J. Neurochem. 42, 878-879, 1984) was used to assist in the assignment of spectra acquired from rat brain homogenates that were obtained from animals killed by cervical fracture or focussed microwave irradiation. Microwave-irradiated brains were divided into four major anatomical regions. Differences in metabolite levels were detected when spectra from fresh tissue and from various regions were compared. The in situ steady-state kinetics of prolidase in whole brain homogenate was determined. The procedure relies on the spectral differences between enzyme substrates and reaction products. The concentration dependence of the rate of hydrolysis of glycyl-L-proline was discribable by the Michaelis-Menten expression with a Michaelis constant of 1.90 mmol L-1 and a maximal velocity of 9.30 mumol min-1 mg-1 protein. The reactions catalysed by glutaminase and acetylcholinesterase in the brain were also monitored.

A proton n.m.r. study of iminodipeptide transport and hydrolysis in the human erythrocyte. Possible physiological roles for the coupled system

The first description of a saturable iminodipeptide transport system present in human erythrocytes is given. The 1H-n.m.r. spectra of glycyl-L-proline and those of free glycine and L-proline are significantly different. This enabled the non-invasive monitoring by 1H-n.m.r. spectroscopy of the hydrolysis of the dipeptide in human erythrocytes and their lysates. The concentration-dependence of the rate of glycyl-L-proline hydrolysis by haemolysates was described by the Michaelis-Menten expression with Km = 14.1 +/- 2.4 mmol/litre and Vmax. = 130 +/- 10 mmol/h per litre of cell water. At concentrations of the dipeptide that saturated prolidase, hydrolysis of glycyl-L-proline by whole cells was approximately 130 times slower than by lysates. This rate difference indicated that transport is the rate-determining step in peptide hydrolysis by whole cells, and thus the concentration-dependence of the transport rate was determined. The membrane transport system was found to be saturable and could be described by the Michaelis-Menten expression with Kt = 4.7 +/- 0.4 mmol/litre and Vmax. = 0.997 +/- 0.026 mmol/h per litre of cell water. Numerical integration of a consistent set of differential rate equations that described a minimal model of the coupled transport-hydrolysis system successfully described prolonged time courses of peptide hydrolysis by whole cells. The simulations showed very low steady-state levels of dipeptide in the erythrocyte and very small lag periods (less than 5 min) in the progress curve describing the appearance of free amino acid inside the cells. The rates of transport of glycyl-L-proline into erythrocytes and kidney proximal-tubular epithelium were compared and the possible importance of erythrocyte prolidase in whole-body prolyl-peptide turnover is discussed.

Prolidase and prolidase deficiency

Prolidase deficiency seems to be a rather rare metabolic disorder. However, many new cases can be detected because screening is easy to perform and enzymatic confirmation allows the differentiation from other iminodipeptidurias . Clinical symptoms are briefly reviewed, while biological considerations and prolidase properties are exhaustively described. Methods for investigating urinary iminodipeptides are given with results. Moreover, several collagen modifications observed in this disorder led us to formulate a hypothesis for their mechanism. Genetic considerations and treatment attempts are discussed.

Prolidase deficiency

The clinical and biochemical findings in a four-year-old girl with prolidase deficiency, treated with L-proline, manganese and ascorbic acid, are presented.

Optimal conditions for prolidase assay by proline colorimetric determination: application to iminodipeptiduria

Prolidase assay was reinvestigated by determining proline, using Chinard's method. Although several authors had previously tested this colorimetric reaction, accurate details regarding enzyme activity were not available. The need for greater sensitivity led to the introduction of several modifications: dialysis was eliminated and the substrate concentration and incubation time were changed. In addition, the reaction mixture was preincubated with Mn2+ for 24 h in order to triple prolidase activity. Color development followed at 90 degrees C, because of partial glycylproline hydrolysis at higher temperatures. The effect of several divalent cations on prolidase activity were tested with and without Mn2+. This modified assay was applied to erythrocytes, plasma and skin fibroblasts from a female patient with iminodipeptiduria.

Prolidase deficiency with imidodipeptiduria. A familial case with and without clinical symptoms

A 23-year-old female with chronic leg ulcer was found to excrete the massive imidopeptides, among which Asp-Pro, Glu-Pro and Gly-Pro were identified. Essentially no prolidase activity was measured in her erythrocytes, while prolinase activity was within a normal range. Her 26-year-old brother also showed imidopeptiduria and erythrocyte prolidase deficiency, but no clinical symptoms were observed. Erythrocytes from her father and 30-year-old brother, who excreted no significant amounts of imidodipeptides, showed intermediate values for the prolidase activity between those for the patient and for normal adults, suggesting that they are heterozygous for this autosomal recessive disorder.