Plasma and Erythrocyte Prolidase Enzyme Kinetics as Functional Biomarkers of Extracellular Matrix Remodeling in Polycystic Ovary Syndrome

Abstract

Background: Polycystic ovary syndrome (PCOS) is a complex endocrine and metabolic disorder characterized by hyperandrogenism, chronic anovulation, insulin resistance, and reproductive dysfunction. Increasing evidence suggests that extracellular matrix (ECM) remodeling and ovarian fibrosis are integral components of PCOS pathophysiology. Prolidase (peptidase D; PEPD), the key enzyme responsible for the final step of collagen degradation, plays a pivotal role in collagen turnover and ECM homeostasis. Although altered prolidase concentrations have been reported in women with PCOS, little is known about the functional kinetic behavior of the enzyme in different biological compartments.
Objective: This study aimed to evaluate plasma and erythrocyte prolidase enzyme kinetics in women with PCOS and to determine whether alterations in Michaelis–Menten kinetic parameters could serve as functional biomarkers of extracellular matrix remodeling and ovarian fibrosis.
Methods: A case–control study was conducted involving 120 women aged 18–40 years, including 60 women diagnosed with PCOS according to the updated Rotterdam ESHRE/ASRM criteria and 60 age- and body mass index-matched healthy controls. Plasma and erythrocyte hemolysates were prepared from fasting venous blood samples. Prolidase activity was determined spectrophotometrically using glycyl-L-proline as the substrate at different substrate concentrations. Michaelis–Menten and Lineweaver–Burk analyses were performed to determine the Michaelis constant (Km) and maximum reaction velocity (Vmax) in plasma and erythrocyte compartments. Hormonal, metabolic, and lipid parameters were evaluated using standard laboratory methods to characterize the clinical phenotype of the study population.
Results: Women with PCOS demonstrated marked alterations in prolidase enzyme kinetics compared with healthy controls. Plasma prolidase exhibited a lower Km value (25.64 vs. 28.57 mM), indicating increased substrate affinity, accompanied by a marked reduction in Vmax (16.54 vs. 30.62 μmol proline min⁻¹ mg⁻¹), suggesting impaired catalytic capacity. In contrast, erythrocyte prolidase showed an increased Km (38.46 vs. 29.41 mM) together with a reduced Vmax (46.96 vs. 58.01 μmol proline min⁻¹ mg⁻¹), reflecting diminished substrate affinity and catalytic efficiency. These compartment-specific kinetic alterations indicate that prolidase dysfunction in PCOS extends beyond changes in enzyme concentration and involves fundamental modifications in enzyme behavior.
Conclusions: The present findings demonstrate that women with PCOS exhibit significant functional alterations in prolidase enzyme kinetics in both plasma and erythrocyte compartments. These kinetic abnormalities may reflect disturbed collagen turnover, extracellular matrix remodeling, and progressive ovarian fibrosis. Assessment of prolidase kinetic parameters provides functional information beyond conventional enzyme measurements and may represent a promising biomarker for evaluating extracellular matrix dysregulation in women with PCOS.