Albumin Is a Component of the Esterase Status of Human Blood Plasma

Probing the effect of glycation on the pseudo-esterase activity of Human Serum Albumin

Human Serum Albumin (HSA), a major protein in blood plasma, exhibits pseudo-enzymatic activity such as pseudo-esterase activity. This study explores the impact of glycation on the pseudo-esterase activity of HSA. Glycation, a non-enzymatic reaction between reducing sugars and HSA was induced using glucose, fructose, and ribose. Glycated HSA samples (gHSA, fHSA, and rHSA) were analyzed for their pseudo-esterase activity using p-nitrophenyl acetate (PNPA) as a substrate. The kinetics of the enzyme-substrate reaction were studied, and structural changes monitored through UV-Vis, fluorescence, and circular dichroism (CD) spectroscopy. Glycation was confirmed using Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-ToF) mass spectrometry. Results indicated a significant reduction in the pseudo-esterase activity of glycated HSA compared to native HSA. Ribose-induced glycation exhibited the highest reduction in activity, attributed to the higher glycation efficiency of ribose. Fluorescence studies revealed changes in Trp fluorescence, suggesting conformational alterations in glycated as well as acetylated HSA. CD spectroscopy confirmed secondary structural changes upon glycation, followed by acetylation. A binding study was conducted to deduce the effect of glycation and acetylation of HSA on its binding activity. These findings highlight the significance of understanding how glycation modifies the biochemical properties of HSA, impacting its physiological roles and therapeutic applications in metabolic disorders. Our studies specifically reveal that glycation impairs the pseudo-esterase activity and alters the drug-binding properties of HSA.

Albumin Is an Integrative Protein of Blood Plasma and Beyond

Albumin is a major protein in mammalian blood plasma or serum, where its concentration in healthy organisms is about 600 μM [...].

Modulation of Albumin Esterase Activity by Warfarin and Diazepam

Data are accumulating on the hydrolytic activity of serum albumin towards esters and organophosphates. Previously, with the help of the technology of proton nuclear magnetic resonance (1H NMR) spectroscopy, we observed the yield of acetate in the solution of bovine serum albumin and p-nitrophenyl acetate (NPA). Thus, we showed that albumin possesses true esterase activity towards NPA. Then, using the methods of molecular docking and molecular dynamics, we established site Sudlow I as the catalytic center of true esterase activity of albumin. In the present work, to expand our understanding of the molecular mechanisms of albumin pseudoesterase and true esterase activity, we investigated-in experiments in vitro and in silico-the interaction of anticoagulant warfarin (WRF, specific ligand of site Sudlow I) and benzodiazepine diazepam (DIA, specific ligand of site Sudlow II) with albumins of different species, and determined how the binding of WRF and DIA affects the hydrolysis of NPA by albumin. It was found that the characteristics of the binding modes of WRF in site Sudlow I and DIA in site Sudlow II of human (HSA), bovine (BSA), and rat (RSA) albumins have species differences, which are more pronounced for site Sudlow I compared to site Sudlow II, and less pronounced between HSA and RSA compared to BSA. WRF competitively inhibits true esterase activity of site Sudlow I towards NPA and does not affect the functioning of site Sudlow II. Diazepam can slow down true esterase activity of site Sudlow I in noncompetitive manner. It was concluded that site Sudlow I is more receptive to allosteric modulation compared to site Sudlow II.

Human Plasma Butyrylcholinesterase Hydrolyzes Atropine: Kinetic and Molecular Modeling Studies

The participation of butyrylcholinesterase (BChE) in the degradation of atropine has been recurrently addressed for more than 70 years. However, no conclusive answer has been provided for the human enzyme so far. In the present work, a steady-state kinetic analysis performed by spectrophotometry showed that highly purified human plasma BChE tetramer slowly hydrolyzes atropine at pH 7.0 and 25 °C. The affinity of atropine for the enzyme is weak, and the observed kinetic rates versus the atropine concentration was of the first order: the maximum atropine concentration in essays was much less than Km. Thus, the bimolecular rate constant was found to be kcat/Km = 7.7 × 104 M-1 min-1. Rough estimates of catalytic parameters provided slow kcat < 40 min-1 and high Km = 0.3-3.3 mM. Then, using a specific organophosphoryl agent, echothiophate, the time-dependent irreversible inhibition profiles of BChE for hydrolysis of atropine and the standard substrate butyrylthiocholine (BTC) were investigated. This established that both substrates are hydrolyzed at the same site, i.e., S198, as for all substrates of this enzyme. Lastly, molecular docking provided evidence that both atropine isomers bind to the active center of BChE. However, free energy perturbations yielded by the Bennett Acceptance Ratio method suggest that the L-atropine isomer is the most reactive enantiomer. In conclusion, the results provided evidence that plasma BChE slowly hydrolyzes atropine but should have no significant role in its metabolism under current conditions of medical use and even under administration of the highest possible doses of this antimuscarinic drug.

Relationship Between Pulmonary Artery Pressure and Inflammation Parameters

Background Inflammation can play a role in the development and progression of pulmonary hypertension (PHT). In this study, inflammatory parameters were compared in congestive heart failure (CHF) patients with and without PHT. The relationship between pulmonary artery pressure (PAP) and inflammatory parameters was investigated. Materials and methods Out of 80 CHF patients, 40 had PHT. The patients' age, gender, smoking status, comorbidities such as diabetes mellitus (DM) and hypertension (HT), and mortality rates were recorded. Inflammatory parameters were recorded. Results The mean age of the PHT group was 64.38 ± 9.17 and the mean age of the non-PHT group was 64.70 ± 8.99. There were 23 men and 17 women in the PHT group, and there were 21 men and 19 women in the non-PHT group. There was no significant difference between the two groups in terms of mean age and gender distribution (p = 0.874 and p = 0.653). Accordingly, the C-reactive protein to albumin ratio (CAR) value was statistically significantly higher in PHT patients (p = 0.023). The eosinophil count was found to be significantly higher in non-PHT patients (p = 0.015). Accordingly, a significant correlation was detected between CAR and PAP (r = 0.392 and p < 0.001). Conclusion In this study, the positive correlation between PAP and CAR and the significantly higher CAR value in PHT patients indicate the presence of inflammation in PHT patients. Studies on the relationship between inflammation and mortality in PHT patients may contribute more to the literature in the future.

Searching for New Biomarkers to Assess COVID-19 Patients: A Pilot Study

During the initial diagnosis of urgent medical conditions, which include acute infectious diseases, it is important to assess the severity of the patient's clinical state as quickly as possible. Unlike individual biochemical or physiological indicators, derived indices make it possible to better characterize a complex syndrome as a set of symptoms, and therefore quickly take a set of adequate measures. Recently, we reported on novel diagnostic indices containing butyrylcholinesterase (BChE) activity, which is decreased in COVID-19 patients. Also, in these patients, the secretion of von Willebrand factor (vWF) increases, which leads to thrombosis in the microvascular bed. The objective of this study was the determination of the concentration and activity of vWF in patients with COVID-19, and the search for new diagnostic indices. One of the main objectives was to compare the prognostic values of some individual and newly derived indices. Patients with COVID-19 were retrospectively divided into two groups: survivors (n = 77) and deceased (n = 24). According to clinical symptoms and computed tomography (CT) results, the course of disease was predominantly moderate in severity. The first blood sample (first point) was taken upon admission to the hospital, the second sample (second point)-within 4-6 days after admission. Along with the standard spectrum of biochemical indicators, BChE activity (BChEa or BChEb for acetylthiocholin or butyrylthiocholin, respectively), malondialdehyde (MDA), and vWF analysis (its antigen level, AGFW, and its activity, ActWF) were determined and new diagnostic indices were derived. The pooled sensitivity, specificity, and area under the receiver operating curve (AUC), as well as Likelihood ratio (LR) and Odds ratio (OR) were calculated. The level of vWF antigen in the deceased group was 1.5-fold higher than the level in the group of survivors. Indices that include vWF antigen levels are superior to indices using vWF activity. It was found that the index [Urea] × [AGWF] × 1000/(BChEb × [ALB]) had the best discriminatory power to predict COVID-19 mortality (AUC = 0.91 [0.83, 1.00], p < 0.0001; OR = 72.0 [7.5, 689], p = 0.0002). In addition, [Urea] × 1000/(BChEb × [ALB]) was a good predictor of mortality (AUC = 0.95 [0.89, 1.00], p < 0.0001; OR = 31.5 [3.4, 293], p = 0.0024). The index [Urea] × [AGWF] × 1000/(BChEb × [ALB]) was the best predictor of mortality associated with COVID-19 infection, followed by [Urea] × 1000/(BChEb × [ALB]). After validation in a subsequent cohort, these two indices could be recommended for diagnostic laboratories.

Drug and pro-drug substrates and pseudo-substrates of human butyrylcholinesterase

Butyrylcholinesterase (BChE) is present in plasma and numerous cells and organs. Its physiological function(s) is(are) still unclear. However, this enzyme is of pharmacological and toxicological importance. It displays a broad specificity and is capable of hydrolyzing a wide range of substrates with turnovers differing by several orders of magnitude. Nowaday, these substrates include more than two dozen carboxyl-ester drugs, numerous acetylated prodrugs, and transition state analogues of acetylcholine. In addition, BChE displays a promiscuous hydrolytic activity toward amide bonds of arylacylamides, and slowly hydrolyzes carbamyl- and phosphoryl-esters. Certain pseudo-substrates like carbamates and organophosphates are major drugs of potential medical interest. The existence of a large genetic poly-allelism, affecting the catalytic properties of BChE is at the origin of clinical complications in the use of certain drugs catabolized by BChE. The number of drugs and prodrugs hydrolyzed by BChE is expected to increase in the future. However, very few quantitative data (Km, kcat) are available for most marketed drugs, and except for myorelaxants like succinylcholine and mivacurium, the impact of BChE genetic mutations on catalytic parameters has not been evaluated for most of these drugs.

The Relationship Between C-reactive Protein Albumin Ratio and Long-Term Mortality in Patients With Acute Coronary Syndrome

Background Coronary artery disease (CAD) is one of the leading causes of death worldwide. CRP/albumin ratio is a sensitive indicator of inflammatory status. It has been shown that this parameter may be associated with poor short-term outcomes in CAD. In this study, we investigated the relationship between long-term mortality and the CRP/albumin ratio in patients with acute coronary syndromes (ACS). Material and methods This study was conducted on patients who applied to our hospital between January 2015 and December 2019 and were diagnosed with ACS. A total of 1689 patients were included in the study. Patients were divided into two groups according to mortality status, and long-term mortality predictors were investigated. Results The average follow-up period was 38.9±10.3 months. The mean age of the entire study group was 56.6±12.2 years, and 1440 (80.5%) of the patients were male. Comorbid diseases and blood parameters were significant between the two groups. In the regression analysis, creatine, hemoglobin, white blood cell count (WBC), neutrophil-lymphocyte ratio (NLR), and CRP albumin ratio (CAR) were found to be independent predictors. In the ROC analysis, it was observed that CAR had the best predictive value. Discussion An increased CAR level is an independent predictor of long-term mortality in ACS patients. It can be used in both short-term and long-term risk stratification for ACS patients.

Time-Resolved Fluorescence Spectroscopy of Blood, Plasma and Albumin as a Potential Diagnostic Tool for Acute Inflammation in COVID-19 Pneumonia Patients

Fluorescence lifetime measurements of blood or plasma offer valuable insights into the microenvironment and molecular interactions of fluorophores, particularly concerning albumin. Neutrophil- and hypoxia-induced oxidative stress in COVID-19 pneumonia patients leads to hyperinflammation, various oxidative modifications of blood proteins, and potential alterations in the fluorescence lifetime of tryptophan-containing proteins, especially albumin. The objective of this study was to investigate the efficacy of time-resolved fluorescence spectroscopy of blood and plasma as a prompt diagnostic tool for the early diagnosis and severity assessment of COVID-19-associated pneumonia. This study examined a cohort of sixty COVID-19 patients with respiratory symptoms. To investigate whether oxidative stress is the underlying cause of the change in fluorescence lifetime, human serum albumin was treated with chloramine T. The time-resolved spectrometer Life Spec II (Edinburgh Instruments Ltd., Livingston, UK), equipped with a sub-nanosecond pulsed 280 nm diode, was used to measure the fluorescence lifetime of blood and plasma. The findings revealed a significant reduction in the fluorescence lifetime of blood (diluted 200 times) and plasma (diluted 20 times) at 360 nm in COVID-19 pneumonia patients compared with their respective values recorded six months post-infection and those of healthy individuals. Significant negative correlations were observed between the mean fluorescence lifetime of blood and plasma at 360 nm and several severity biomarkers and advanced oxidation protein products, while a positive correlation was found with albumin and the albumin-globulin ratio. The time-resolved fluorescence spectroscopy method demonstrates the potential to be used as a preliminary screening technique for identifying patients who are at risk of developing severe complications. Furthermore, the small amount of blood required for the measurements has the potential to enable a rapid fingerstick blood test.

Serum Albumin in Health and Disease: From Comparative Biochemistry to Translational Medicine

Being one of the main proteins in the human body and many animal species, albumin plays a decisive role in the transport of various ions, electrically neutral molecules and in maintaining the colloid osmotic pressure of the blood [...].