Prolidase activity in serum and pleural fluids in patients with tuberculous pleural effussion

PROLIDASE: A Review from Discovery to its Role in Health and Disease

Prolidase (peptidase D), encoded by the PEPD gene, is a ubiquitously expressed cytosolic metalloproteinase, the only enzyme capable of cleaving imidodipeptides containing C-terminal proline or hydroxyproline. Prolidase catalyzes the rate-limiting step during collagen recycling and is essential in protein metabolism, collagen turnover, and matrix remodeling. Prolidase, therefore plays a crucial role in several physiological processes such as wound healing, inflammation, angiogenesis, cell proliferation, and carcinogenesis. Accordingly, mutations leading to loss of prolidase catalytic activity result in prolidase deficiency a rare autosomal recessive metabolic disorder characterized by defective wound healing. In addition, alterations in prolidase enzyme activity have been documented in numerous pathological conditions, making prolidase a useful biochemical marker to measure disease severity. Furthermore, recent studies underscore the importance of a non-enzymatic role of prolidase in cell regulation and infectious disease. This review aims to provide comprehensive information on prolidase, from its discovery to its role in health and disease, while addressing the current knowledge gaps.

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.

Maternal plasma prolidase, matrix metalloproteinases 1 and 13, and oxidative stress levels in pregnancies complicated by preterm premature rupture of the membranes and chorioamnionitis

OBJECTIVE

This study aimed to investigate the role of various biochemical markers in preterm premature rupture of membranes (PPROM) and in prediction of chorioamnionitis in patients with PPROM.

MATERIAL AND METHODS

This case-control study included a total of 100 pregnant women at 26-34 gestational weeks. Of these women, 50 were healthy and 50 had PPROM. The biochemical markers in the maternal plasma including prolidase, matrix metalloproteinase (MMP) 1 and 13, total oxidative status (TOS), total antioxidant capacity (TAC), glutathione peroxidase (GPx), catalase (CAT), paraoxonase-1 (PON-1), tumor necrosis factor alpha (TNF-α), and high sensitive C-reactive protein (hs-CRP) were assayed. These levels were compared between the PPROM and control groups and between women with or without chorioamnionitis in the PPROM group.

RESULTS

Compared to the control group, the levels of prolidase, MMP-13, and TOS were significantly higher (p values <0.001, 0.020, and 0.035, respectively) and those of TAC and PON-1 were significantly lower in the maternal plasma of the PPROM group (p values=0.012 and <0.001, respectively). The plasma prolidase and TOS levels were significantly higher (p values=0.033 and 0.005, respectively) and the plasma TAC and PON-1 levels were significantly lower in women with chorioamnionitis as compared with the corresponding values in women without chorioamnionitis in the PPROM group (p values =0.041 and 0.048, respectively). The multivariate logistic regression analysis observed that prolidase, TAC, and PON-1 were important markers for the presence of PPROM and prolidase and TOS were important markers for predicting chorioamnionitis.

CONCLUSION

This study suggested that maternal plasma prolidase, TAC, and PON-1 may be useful for the diagnosis of PPROM, and prolidase and TOS may be used to predict chorioamnionitis in patients with PPROM.

Serum prolidase activity in patients with pulmonary tuberculosis

AIM

To investigate serum prolidase activity (SPA) in patients with pulmonary tuberculosis (PTB).

MATERIAL AND METHODS

Twenty-nine PTB patients and 32 controls were included in the study. PTB patients (cavitary and non-cavitary) and controls were compared in terms of mean SPA. Correlations were evaluated between SPA and acute phase reactants.

RESULTS

Mean SPA was significantly higher in PTB patients than in the control group. Mean SPA was significantly higher in patients with cavitary TB than non-cavitary TB. Mean SPA in patients with mild PTB was lower than patients with moderate and severe disease. We found significant correlations between SPA and CRP, ESR, albumin, platelet counts, HDL-cholesterol and LDH activity.

CONCLUSION

This study has shown that PTB patients have higher SPA than controls. The increase in SPA might be related to tissue destruction, increased immunoglobulin, complement levels and increased fibroblastic activity; all of which are involved in the natural history of PTB.

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.