Prolidase deficiency

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.

Prolidase - A protein with many faces

Prolidase is a metal-dependent peptidase specialized in the cleavage of dipeptides containing proline or hydroxyproline on their C-termini. Prolidase homologues are found in all kingdoms of life. The importance of prolidase in human health is underlined by a rare hereditary syndrome referred to as Prolidase Deficiency. A growing number of studies highlight the importance of prolidase in various other human conditions, including cancer. Some recent studies link prolidase's activity-independent regulatory role to tumorigenesis. Furthermore, the enzyme or engineered variants have some applications in biotechnology. In this short review, we aim to highlight different aspects of the protein the importance of which is increasingly recognized over the last years.

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: 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.

Biodegradable microspheres for prolidase delivery to human cultured fibroblasts

Prolidase deficiency (PD) is a rare autosomal recessive disorder caused by inadequate levels of the cytosolic exopeptidase prolidase (E.C. 3.4.13.9), for which there is not, as yet, a resolutive cure. We have investigated whether biodegradable microspheres loaded with prolidase could release active enzyme inside cells, to consider this system as a possible therapeutic approach for prolidase deficiency. Poly(lactide-co-glycolide) microspheres were prepared, modifying the classical double emulsion solvent evaporation method to mitigate the burst effect of the enzyme from the microspheres. Ex-vivo experiments were performed, by incubating microencapsulated prolidase with cultured fibroblasts from PD patients and from controls, to determine the amount of active enzyme delivered to the cells. The microparticulate drug delivery system described carried small amounts of active prolidase inside fibroblasts, ensuring a response to the intracellular accumulation of X-Pro dipeptides, the mechanism that is supposed to be responsible for the development of clinical manifestations of this disorder in man. A positive result of the presence of active enzyme inside cells was an improvement in fibroblast shape.

Characterization of prolidase I and II purified from normal human erythrocytes: comparison with prolidase in erythrocytes from a patient with prolidase deficiency

The effect of various sulfur-containing amino acids on the activities of prolidase isoenzymes I and II isolated from erythrocytes of healthy individuals, and erythrocyte lysates from a patient with prolidase deficiency was investigated. The activity of prolidase I against glycylproline was strongly enhanced by D: -methionine. L: -Methionine and D: ,L: -methionine slightly enhanced the activity at low concentration, but N-acetyl-L: -methionine had no effect. D: -Ethionine, L: -ethionine, and D: ,L: -ethionine also enhanced the activity of prolidase I. D: ,L: -Homocysteine enhanced the activity at low concentration, but inhibited the activity at 50 mM: . The activity of prolidase II against methionylproline was enhanced by D: -methionine, D: ,L: -methionine, and L: -methionine, but N-acetyl-L: -methionine had no effect. D: -Ethionine and D: ,L: -ethionine strongly enhanced the activity of prolidase II compared with L: -ethionine; D: ,L: -homocysteine weakly enhanced the activity. D: ,L: -Homocysteine-thiolactone inhibited the activities of prolidase I and II in a concentration-dependent manner. The effect of various sulfur-containing amino acids on prolidase activity against methionylproline in erythrocyte lysates from a patient with prolidase deficiency was almost the same as that on prolidase II. The kinetics of the activities of prolidase I, II, and patient prolidase were also studied. Their K (m) values were changed by adding sulfur-containing amino acids, but V (max) values were unchanged.

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.

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.

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 prolidase activity in erythrocytes from a patient with prolidase deficiency: Comparison with prolidase I and II purified from normal human erythrocytes

OBJECTIVES

The purpose of this study was to investigate the effect of various amino acids and their metabolites on the activities of prolidase I and II from human erythrocytes compared to those in a patient with prolidase deficiency.

DESIGN AND METHODS

Prolidase I and II from human erythrocytes were purified by using column chromatography. Prolidase activity against various iminodipeptides was determined by spectrophotometry using Chinard's method.

RESULTS

The activities of prolidase I and II against glycylproline and methionylproline were enhanced by glycine, L- and D-isoforms of alanine and serine and D-isoforms of valine, leucine and isoleucine. L-isoforms of branched amino acids inhibited the activity of prolidase I. On the other hand, the activity of prolidase II was enhanced by all of these L-branched amino acids. The patient's prolidase activity was also enhanced by all the L- and D-branched amino acids.

CONCLUSION

The activities of prolidase I and II against various iminodipeptides were prominently enhanced by glycine, but the effect of L-valine differed between the two enzymes. Enzymatic properties of the patient's prolidase were essentially the same as those of prolidase II.

Intracellular delivery of liposome-encapsulated prolidase in cultured fibroblasts from prolidase-deficient patients

Prolidase is a cytosolic exopeptidase whose deficiency causes the development of a rare autosomal recessive disorder known as Prolidase Deficiency (PD). The main manifestations of PD are intractable ulcerations of the skin, recurrent infections and mental retardation. At this time only a hazardous and expensive chronic therapy based on blood transfusions is the suggested treatment for PD. The aim of this work was to investigate the capability of utilizing liposomes as enzyme carriers: these vesicular systems have been recently evaluated as protein carriers for their potential in terms of "in vivo" localization, drug release and for protein stabilization in biological fluids. Liposomes were prepared, with a 1:1 PC:Col molar ratio with or without DSPE-PEG, by a thin-film hydration. Ex-vivo experiments were performed, incubating prolidase loaded liposomes with cultured fibroblasts from PD patients and from controls, to determine the amount of active enzyme delivered to cells. Evaluation of liposomes toxicity on cultured skin fibroblasts showed that liposomes did not interfere with cellular growth. Results showed that all the active prolidase encapsulated in the liposomes was completely vehiculated inside fibroblasts after 6 days incubation. SEM analysis suggests that prolidase is vehiculated inside the cell through liposome endocytosis.

Effects of amino acids and its metabolites on prolidase activity against various iminodipeptides in erythrocytes from normal human and a patient with prolidase deficiency

BACKGROUND

The characteristics of prolidase in erythrocytes from controls and patient with prolidase deficiency were investigated.

METHODS

The erythrocytes were isolated from the heparinized blood of normal human and a patient with prolidase deficiency. Effects of various amino acids and their metabolites on prolidase activity against iminodipeptides in presence of 1 mmol/l MnCl(2) were investigated.

RESULTS

Prolidase activity against glycylproline in erythrocytes from normal human was strongly enhanced by glycine, L-alanine, L-serine with MnCl(2), but the activity was strongly inhibited by L-valine, and L-leucine. However, the stereoisomers, D-leucine and D-valine enhanced the activity. The prolidase activity against methionylproline in erythrocytes from the patient with prolidase deficiency was also enhanced by glycine, L-alanine and L-serine. The activity was inhibited by l-leucine, but D-leucine and L-valine enhanced the activity against various iminodipeptides.

CONCLUSION

Prolidase activity against glycylproline in normal human erythrocytes and against methionylproline from the prolidase-deficient patient was enhanced strongly by glycine, alanine and serine with MnCl(2). However, this activity was inhibited by L-leucine, but was enhanced by D-leucine.

Characteristics of prolinase against various iminodipeptides in erythrocyte lysates from a normal human and a patient with prolidase deficiency

The effect of various amino acids and MnCl

The kinetics of prolinase activity in the erythrocytes from both the normal individual and the prolidase-deficient patient were also studied. Their K

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.

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.

Prolidase deficiency: a multisystemic hereditary disorder

Prolidase deficiency is a rare hereditary disorder with a wide spectrum of clinical manifestations including skin ulcers, eczematous eruptions, characteristic facies, mental retardation, splenomegaly, and susceptibility to infections. We report two new cases of prolidase deficiency. Our patients had the typical manifestations of prolidase deficiency. One also had lupus erythematosus. Prolidase activity was either normal or half-normal in all family members. The skin disease in our patients did not respond to topical glycine/proline ointment or to oral vitamin C.

Prolidase deficiency: a case report and literature review

We describe a patient in whom chronic leg ulceration was due to prolidase deficiency. The clinical features of this condition are described and we discuss the metabolic abnormality and the treatment regimes which have been employed. We also report the further finding of erosive cystitis, which we consider should be added to the list of clinical features of prolidase deficiency.

Cell density affects prolidase and prolinase activity and intracellular amino acid levels in cultured human cells

Prolidase (EC 3.4.13.9) and prolinase (EC 3.4.13.8) and intracellular amino acid levels in cultured human cells increased when cell density rose. Firstly, two normal fibroblast strains were continuously cultured for 21 days and these parameters were measured on days 3, 7, 10, 14, 17 and 21 after plating. Prolidase, prolinase and amino acid levels varied considerably depending on the duration of culture and growth rate. Secondly, we studied the action of different cadmium and cobalt concentrations on prolidase activity. These two effectors altered this enzyme activity, but secondarily to modifying cell density. Thirdly, prolidase activity was investigated in 8 control amniotic cell strains, with a view to prenatal diagnosis of inherited prolidase deficiency, and we noted the same cell density interference. Due to the large variations related to cell density, we recommend specifying the number of cells per unit surface, and avoiding the term 'cells at confluency' which is unduly vague.

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.

Presence in human cells and tissues of two prolidases and their alteration in prolidase deficiency

Two forms of prolidase can be separated for all the human cells and tissues examined by DEAE-cellulose column chromatography or batch methods. Serum had a very low prolidase activity eluting as a single peak prior to tissue peak I prolidase. Analysis of the two peaks can readily be carried out using white blood cells, cultured skin fibroblasts and amniotic fluid cells. Dialysis inactivated peak II prolidase although the loss can be prevented by the presence of dithiothreitol. The two peaks differed in their response to Mn(2+), substrate specificity, heat stability and inhibition by p-hydroxymercuribenzoate. In two unrelated cases of prolidase deficiency, fibroblast peak I was markedly reduced, although still detectable, whereas peak II was active against all the substrates, except for a 90% reduction against glycyl-L-proline. The properties of peak II were altered in the disease. The results imply that the two forms of prolidase are structurally related.

Clinical and biochemical characteristics of prolidase deficiency in siblings

Two brothers with recurrent skin ulcers of the lower limbs, subnormal intelligence, developmental abnormalities, and poliosis were found to excrete large quantities of several imidodipeptides in their urine. Glycylproline was the most prominent imidodipeptide excreted and was also detected in their blood. Prolidase activity was markedly deficient in red blood cells from both patients (4.1% and 3.7% of control mean) and skin fibroblasts from the one brother so examined (3.7% of control mean). A total of 20 patients with prolidase deficiency, including the two in this report, have been described in the literature. Their manifestations and various attempts at treatment are reviewed.