Serum Albumin in Health and Disease: Esterase, Antioxidant, Transporting and Signaling Properties

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 and charged molecules—and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind to almost all known drugs, as well as many nutraceuticals and toxic substances, largely determining their pharmaco- and toxicokinetics. Albumin of humans and respective representatives in cattle and rodents have their own structural features that determine species differences in functional properties. However, albumin is not only passive, but also an active participant of pharmacokinetic and toxicokinetic processes, possessing a number of enzymatic activities. Numerous experiments have shown esterase or pseudoesterase activity of albumin towards a number of endogeneous and exogeneous esters. Due to the free thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. Glycated albumin makes a significant contribution to the pathogenesis of diabetes and other diseases. The interaction of albumin with blood cells, blood vessels and tissue cells outside the vascular bed is of great importance. Interactions with endothelial glycocalyx and vascular endothelial cells largely determine the integrative role of albumin. This review considers the esterase, antioxidant, transporting and signaling properties of albumin, as well as its structural and functional modifications and their significance in the pathogenesis of certain diseases.

The role of proteolysis in the formation of aerated texture in food systems using whey peptides

Сывороточные протеины часто применяются в различных отраслях пищевой индустрии, в частности, благодаря технологическим свойствам, таким как пенообразование, эмульгирование, гелеобразование. Наличие в бета-лактоглобулине, основном белке молочной сыворотки, свободной тиоловой группы определяет его реактивность, в том числе способность к пенообразованию. Способность образовывать пены и стабильность пены не всегда коррелируют, так как они проистекают под влиянием различных межмолекулярных взаимодействий. Во многом эти свойства зависят от молекулярно-массового распределения белков (ММР), а следовательно, одним из инструментов их регулирования можно считать биокаталитическую конверсию. В работе были исследованы физико-химические свойства гидролизата сывороточных белков и продуктов его фракционирования на ультрафильтрационной мембране. Проведен анализ влияния ММР на пенообразование и стойкость пен. Оценка ММР показала высокое содержание низкомолекулярных пептидов (95,8 %) в пермеате в сравнении с исходным гидролизатом (43,34 %). Кратность пены и пенообразующая способность всех образцов находились примерно на одном уровне в диапазоне 2,9-3,1 усл. ед. и 65,5-67,7 % соответственно. При этом наибольшее значение стойкости пены соответствовало пермеату (125 мин). Наихудшие показатели стойкости выявлены у образцов гидролиза и его концентрата. Основываясь на данных, представленных в статье, можно сделать вывод о том, что высокая пенообразующая способность как концентратов, так и гидролизатов, не гарантирует в итоге получение требуемого результата, при этом для получения стойких пенных масс с высокой кратностью пены в белковых растворах должно присутствовать большое количество пептидов молекулярной массой менее 5 кДа или более 10 кДа. Whey proteins are often used in various sectors of the food industry, in particular, due to technological properties such as foaming, emulsification, gelation. The presence of a free thiol group in beta-lactoglobulin, the main protein of milk whey, determines its reactivity, including the ability to foam. The ability to form foams and foam stability do not always correlate, as they occur under the influence of various intermolecular interactions, in many respects these properties depend on the molecular weight distribution of proteins (MWD), and, therefore, biocatalytic conversion can be considered one of the tools for their regulation. The work investigated the physicochemical properties of whey protein hydrolyzate and products of its fractionation on an ultrafiltration membrane. The analysis of the effect of MWD on foaming and foam stability has been carried out. Evaluation of MWD showed a high content of low molecular weight peptides (95.8 %) in the permeate in comparison with the initial hydrolyzate (43.34 %). The multiplicity of foam and the foaming ability of all samples was approximately at the same level in the range of 2.9-3.1 conventional units and 65.5-67.7 %, respectively. In this case, the highest value of foam stability corresponded to the permeate (125 min.). The worst resistance indicators were found in samples of hydrolysis and its concentrate. Based on the data presented in the article, it can be concluded that the high foaming capacity of both concentrates and hydrolysates does not ultimately guarantee the production of stable foam masses, while in order to obtain stable foam masses with a high foam expansion, protein solutions must be present a large number of peptides with a molecular weight of less than 5 kDa or more than 10 kDa.

Serum Albumin

Being one of the most abundant proteins in human and other mammals, albumin plays a crucial role in transporting various endogenous and exogenous molecules and maintaining of colloid osmotic pressure of the blood. It is not only the passive but also the active participant of the pharmacokinetic and toxicokinetic processes possessing a number of enzymatic activities. A free thiol group of the albumin molecule determines the participation of the protein in redox reactions. Its activity is not limited to interaction with other molecules entering the blood: of great physiological importance is its interaction with the cells of blood, blood vessels and also outside the vascular bed. This entry contains data on the enzymatic, inflammatory and antioxidant properties of serum albumin.

1250. Novel Boronic Acid Transition State Analogs (BATSI) with in vitro inhibitory activity against class A, B and C β-lactamases

Background Catalytic mechanisms of serine β-lactamases (SBL; classes A, C and D) and metallo-β-lactamases (MBLs) have directed divergent strategies towards inhibitor design. SBL inhibitors act as high affinity substrates that -as in BATSIs- form a reversible, dative covalent bond with the conserved active site Ser. MBL inhibitors bind the active-site Zn2+ ions and displace the nucleophilic OH-. Herein, we explore the efficacy of a series of BATSI compounds with a free-thiol group at inhibiting both SBL and MBL. Methods Exploratory compounds were synthesized using stereoselective homologation of (+) pinandiol boronates to introduce the amino group on the boron-bearing carbon atom, which was subsequently acylated with mercaptopropanoic acid. Representative SBL (KPC-2, ADC-7, PDC-3 and OXA-23) and MBL (IMP-1, NDM-1 and VIM-2) were purified and used for the kinetic characterization of the BATSIs. In vitro activity was evaluated by a modified time-kill curve assay, using SBL and MBL-producing strains. Results Kinetic assays revealed that IC50 values ranged from 1.3 µM to >100 µM for this series. The best compound, s08033, demonstrated inhibitory activity against KPC-2, VIM-2, ADC-7 and PDC-3, with IC50 in the low μM range. Reduction of at least 1.5 log10-fold of viable cell counts upon exposure to sub-lethal concentrations of antibiotics (AB) + s08033, compared to the cells exposed to AB alone, demonstrated the microbiological activity of this novel compound against SBL- and MBL-producing E. coli (Table 1). Table 1 Conclusion Addition of a free-thiol group to the BATSI scaffold increases the range of these compounds resulting in a broad-spectrum inhibitor toward clinically important carbapenemases and cephalosporinases. Disclosures Robert A. Bonomo, MD, Entasis, Merck, Venatorx (Research Grant or Support)

Trefoil Factor Family (TFF) Peptides and Their Diverse Molecular Functions in Mucus Barrier Protection and More: Changing the Paradigm

Trefoil factor family peptides (TFF1, TFF2, TFF3) are typically co-secreted together with mucins. Tff1 represents a gastric tumor suppressor gene in mice. TFFs are also synthesized in minute amounts in the immune and central nervous systems. In mucous epithelia, they support rapid repair by enhancing cell migration (“restitution”) via their weak chemotactic and anti-apoptotic effects. For a long time, as a paradigm, this was considered as their major biological function. Within recent years, the formation of disulfide-linked heterodimers was documented for TFF1 and TFF3, e.g., with gastrokine-2 and IgG Fc binding protein (FCGBP). Furthermore, lectin activities were recognized as enabling binding to a lipopolysaccharide of Helicobacter pylori (TFF1, TFF3) or to a carbohydrate moiety of the mucin MUC6 (TFF2). Only recently, gastric TFF1 was demonstrated to occur predominantly in monomeric forms with an unusual free thiol group. Thus, a new picture emerged, pointing to diverse molecular functions for TFFs. Monomeric TFF1 might protect the gastric mucosa as a scavenger for extracellular reactive oxygen/nitrogen species. Whereas, the TFF2/MUC6 complex stabilizes the inner layer of the gastric mucus. In contrast, the TFF3–FCGBP heterodimer (and also TFF1–FCGBP) are likely part of the innate immune defense of mucous epithelia, preventing the infiltration of microorganisms.

SYNTHESIS AND CHARACTERIZATION OF HYDROXYPROPYL CELLULOSE-CYSTEAMINE CONJUGATE AS A NOVEL CATIONIC THIOMER WITH LIPOPHILIC PROPERTIES

Objective: Thiomers have been known as polymer with mucoadhesive properties. The aim of this study was to synthesize the mucoadhesive potential of hydroxypropyl cellulose-cysteamine conjugate (HPC-cysteamine).Methods: The parent polymer HPC was chemically modified by introducing sulphydryl bearing compound using reductive amination. HPC-cysteamine conjugates were prepared at reaction pH value of 5. The reaction was stabilized by the addition of cyanoborohydride. Afterwards, the conjugate was evaluated for optimum free thiol group, swelling behavior, viscosity and mucoadhesive properties.Results: The conjugates showed maximum thiol incorporation on HPC of 1063.03±64.27 µmol/g. The disulphide groups content was 278.71±32.14 μmol/g. Mucoadhesion studies revealed that mucoadhesion of HPC-cysteamine demonstrated 26 h. The swelling behaviour of HPC-cysteamine tablets increased within the time period of study. The viscosity of HPC-cysteamine was higher than that of unmodified HPC. The thermal profile of HPC-cysteamine and unmodified HPC analyzed by differential scanning calorimetry (DSC) displayed a different enthalpy (ΔH) value.Conclusion: HPC-cysteamine conjugate renders better properties which might be more beneficial for drug delivery system compared to unmodified HPC.

Assessment of Plasma Homocysteine Level among Sudanese Rheumatoid Arthritis Patients

Homocysteine (Hcy) is a four-carbon amino acid with a free thiol group, which is formed by demethylation of methionine, together with the help of some vitamins (B12, B6 and folate). The mechanisms responsible for hyperhomocysteinaemia in rheumatoid arthritis (RA) are not clear. However, drugs such as methotrexate has shown to have an effect on homocysteine metabolism, and interfers with vitamin metabolism and absorption. The aim of study was to assess plasma homocysteine level among Sudanese rheumatoid arthritis patients and to correlate homocysteine level with various types of treatment. A case control study was performed in Khartoum state, Sudan. A total of 60 Sudanese were enrolled in this study (30 RA patients and 30 healthy controls), 6 (20%) were males and 24 (80%) were females. Homocysteine levels were assessed using A15 analyzer. The consents were obtained from patients and it was approved by ethical committee of AL Neelain University. The mean SD was determined and then compared between cases group and controls group by calculating the P.value, the data was analyzed using SPSS. Homocysteine was found to be increased in 26 (86.7%) out of 30 RA cases. There was a significant difference in homocysteine level (P-value: 0.000) between cases and controls; with a mean of 24.6, 15.06 μmol/L; respectively. There was a significant in homocysteine levels with different types of treatment (P-value: 0.000). Plasma homocysteine level increases in Rheumatoid arthritis.

Halogenation of β-estradiol by a rationally designed mesoporous biocatalyst based on chloroperoxidase

Chloroperoxidase from Caldariomyces fumago was immobilized in Eupergit® C, a commercial mesoporous acrylic-based material. Due to low stability of the enzyme under neutral and basic pH, the usual covalent immobilization procedures cannot be applied to this enzyme. Several strategies were followed in order to achieve a stable interaction between the protein and the support. The support was efficiently functionalized with different reactive groups such as aromatic and aliphatic amines, glutaraldehyde, diazonium ions, and maleimide moieties; solvent-exposed amino acid residues in chloroperoxidase were identified or created through chemical modification, so that they were reactive under conditions where the enzyme is stable. Enzyme load and retained activity were monitored, obtaining biocatalysts with specific activity ranging from 200 to 25,000 U/g. The highest load and activity was obtained from the immobilization of a chemically-modified CPO preparation bearing a solvent-exposed free thiol group. This biocatalyst efficiently catalyzed the transformation of β-estradiol, an endocrine disruptor.