Hydrolysis of Extracellular Adenine Nucleotides by Human Spermatozoa: Regulatory Role of Ectonucleotidases in Sperm Function

Evidence is presented for the existence of ectonucleotidases on the membrane of intact human spermatozoa. Enzymes hydrolyze extracellular ATP, ADP and AMP and hence could be described as ecto-NTPDase and ecto-5\u27-nucleotidase. Suramin, Cibacron 3GA and DIDS, well known ecto-NTPDase inhibitors, caused inhibition of the observed enzyme activity. Enzymatic hydrolysis of ATP, ADP and AMP follows simple Michaelis-Menten kinetics with similar enzyme affinity for all three substrates (Km for ATP, ADP and AMP were (0.395 ± 0.027), (0.401 ± 0.031), (0.517 ± 0.038) mmole dm−3, respectively). Influence of extracellular ATP, AMP, adenosine and cAMP on the parameters of sperm velocity and acrosome reaction was also examined. In normozoospermic samples, ATP and cAMP induced an increase in the amplitude of lateral head displacement and number of acrosomally reacted cells, but not in sperm velocity. However, adenosine and AMP enhanced sperm velocity, without influencing the acrosome reaction. These results show that ATP and adenosine regulate sperm motility parameters in different ways

Serum activities of adenosine deaminase, dipeptidyl peptidase IV and prolyl endopeptidase in patients with fibromyalgia: diagnostic implications

Fibromyalgia (FM) is a chronic pain syndrome with number of symptoms that present challenge in terms of diagnosis and treatment. Patients with FM show abnormal profile of purines in plasma. In this work, we measured serum activities of enzymes involved in purine metabolism, namely total adenosine deaminase (ADE) and its isoforms (ADE1 and ADE2), ecto- ATPase, and 5′- nucleotidase (5′-NT). We also measured activity of dipeptidyl peptidase IV (DPPIV) and prolyl endopeptidase (PEP). Spectrophotometric and fluorometric methods were used for enzyme activity determinations. Enzyme activities were measured in sera of 24 patients with FM that were not undergoing pharmacological treatment during the study. Control group comprised 32 healthy control subjects. Significantly higher activities of total ADE (P = 0.025) and ADE2 (P = 0.011) were observed in FM patients, while no significant differences in ADE1, ecto-ATPase, and 5′-NT activities (P > 0.05) were found when compared to healthy controls. Moreover, increase in the activity of DPPIV (P = 0.015) and lower activity of PEP (P = 0.011) were also found in the FM group. ROC analysis pointed to different diagnostic sensitivities/specificities for individual enzyme activities measured as follows: ADE (50.0/87.5), ADE2 (41.7/90.6), DPPIV (62.5/71.9), and PEP (83.3/62.5). ADE2 and PEP were shown to be independent predictors of FM, while combination of the two gives AUC of 0.786 (95 % confidence interval of 0.656–0.885, P < 0.05). Our results are showing that serum activities of ADE2 and PEP could be useful as biomarkers for FM diagnosis. However, relatively low diagnostic sensitivity of ADE2 and specificity of PEP must be taken into account