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

The esterase status of blood plasma can claim to be one of the universal markers of various diseases; therefore, it deserves attention when searching for markers of the severity of COVID-19 and other infectious and non-infectious pathologies. When analyzing the esterase status of blood plasma, the esterase activity of serum albumin, which is the major protein in the blood of mammals, should not be ignored. The purpose of this study is to expand understanding of the esterase status of blood plasma and to evaluate the relationship of the esterase status, which includes information on the amount and enzymatic activity of human serum albumin (HSA), with other biochemical parameters of human blood, using the example of surviving and deceased patients with confirmed COVID-19. In experiments in vitro and in silico, the activity of human plasma and pure HSA towards various substrates was studied, and the effect of various inhibitors on this activity was tested. Then, a comparative analysis of the esterase status and a number of basic biochemical parameters of the blood plasma of healthy subjects and patients with confirmed COVID-19 was performed. Statistically significant differences have been found in esterase status and biochemical indices (including albumin levels) between healthy subjects and patients with COVID-19, as well as between surviving and deceased patients. Additional evidence has been obtained for the importance of albumin as a diagnostic marker. Of particular interest is a new index, [Urea] × [MDA] × 1000/(BChEb × [ALB]), which in the group of deceased patients was 10 times higher than in the group of survivors and 26 times higher than the value in the group of apparently healthy elderly subjects.

Esterase Activity of Serum Albumin Studied by 1H NMR Spectroscopy and Molecular Modelling

Serum albumin possesses esterase and pseudo-esterase activities towards a number of endogenous and exogenous substrates, but the mechanism of interaction of various esters and other compounds with albumin is still unclear. In the present study, proton nuclear magnetic resonance (1H NMR) has been applied to the study of true esterase activity of albumin, using the example of bovine serum albumin (BSA) and p-nitrophenyl acetate (NPA). The site of BSA esterase activity was then determined using molecular modelling methods. According to the data obtained, the accumulation of acetate in the presence of BSA in the reaction mixture is much more intense as compared with the spontaneous hydrolysis of NPA, which indicates true esterase activity of albumin towards NPA. Similar results were obtained for p-nitophenyl propionate (NPP) as substrate. The rate of acetate and propionate release confirms the assumption that there is a site of true esterase activity in the albumin molecule, which is different from the site of the pseudo-esterase activity Sudlow II. The results of molecular modelling of BSA and NPA interaction make it possible to postulate that Sudlow site I is the site of true esterase activity of albumin.

[THE QUANTIFICATION OF SULPHATED GLYCOSAMINOGLYCANS IN RAT URINE IN EXPERIMENTAL HEMORRHAGIC CYSTITIS]

The paper presents the study of the excretion of sulfated glycosaminoglycans (GAG) in the urine of rats in experimental hemorrhagic cystitis induced by cyclophosphamide and treated with glycosaminoglycan replacement therapy. Rats were given intraperitoneal injections of cyclophosphamide at a dose of 100 mg per 1 kg body weight and subsequently treated with intragastric administration of the combined preparation of glycosaminoglycans containing glucosamine hydrochloride and chondroitin sulfate at a dose of 10 and 100 mg per 1 kg of body weight. Within 24 or 72 hours after cystitis induction there was a statistically significant increase in urinary GAG excretion. The study also found a decrease (from 1.34 to 1.22 mg/dL) in urinary GAG within 0 to 72 hours following induction of acute cystitis without glycosaminoglycan therapy. In the subchronic model of inflammation in the bladder, upon repeated administration of low doses of cyclophosphamide (50 mg/kg), decrease in urinary GAG within 0 to 72 hours (1,32±0,13 mg/dL) as well as increased excretion after 96 hours at a concentration of 2,29±0,13 mg/L after initiation cystitis were found.

[On necessity to modify biochemical methods for detecting organophosphorus componds in chemical weapons extinction objects (review of literature)]

The article covers problems of biochemical methods assessing organophosphorus toxic compounds in objects of chemical weapons extinction. The authors present results of works developing new, more specific and selective biochemical methods.

[Serum albumin: search for new sites with esterase activity according to molecular modeling data]

It is known that albumin is able to cut ester bonds in organophosphates (OPs). Amino acids responsible for esterase and pseudo-esterase activity of albumin towards OPs are still not determined. The purpose of this study is to identify the potential sites of esterase activity of albumin by the example of its interaction with soman using molecular modeling methods. The structures of the protein complexes with soman was determined by molecular docking procedure, the stability of the complexes were simulated using molecular dynamics method. It has been determined that productive sorption of soman near Tyr411 is possible only after deprotonation of the tyrosine. Tyr150 binds soman more efficiently than Tyr411; deprotonation of Tyr150 does not affect the binding efficiency, but affects on the stability of the complexes. The true esterase activity of albumin Tyr150 in relation to soman is proposed. It is shown that Ser193 can also be responsible for the esterase activity of albumin. We hypothesize that deprotonation of catalytic amino acid in one of the sites could be initiated by ligand binding in other sites (allosteric regulation).