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Implication of Mitochondrial Coenzyme Q10 (Ubiquinone) in Alzheimer’s Disease *
Published in Abhai Kumar, Debasis Bagchi, Antioxidants and Functional Foods for Neurodegenerative Disorders, 2021
Sayantan Maitra, Dibyendu Dutta
The observed rate of electron transfer (Voet) was found to be in hyperbolic relation with the total substrate concentration (ST) in the mitochondrial membrane (Figure 15.3). Vmaxo and Vmaxr are the maximal rate of oxidation and reduction, respectively, of the CoQ pool. Kdo and Kdr are the respective dissociation constants of CoQ pool for the oxidase and reductase. The term in the denominator is an operational Km (Michaelis–Menten constant) of the system ST. Km denotes the substrate concentration when the transfer of electron reaches half of its maximum velocity. Km is the ratio between the rate of overall catalysis and the rate of binding affinity. Hence, the increased value of Km indicates that the enzyme possesses an increased rate of catalysis or decreased enzyme binding affinity to the substrates. However, overall maintenance of enzyme efficiency (rate of enzyme catalysis/Km) is feasible in this context. Consequently, the maximum velocity of electron transfer will only be attained if the substrate concentration is high enough to saturate the enzyme [28,29].
Solute Translocations
Published in Lelio G. Colombetti, Biological Transport of Radiotracers, 2020
The preceding review of processes associated with solute translocation in biological systems is both brief and personal. Some may be offended by my stress (or lack of it) and others, by my including (or excluding) certain topics in the framework of the discourse. As an investigator concerned with biological transport, I am frequently disturbed by the lack of respect often given the subject both within and without the laboratory. To study enzyme catalysis in an unmixed solution or in the presence of competing substrates would clearly be absurd. Yet, I have often seen a study involving tissue or cell incubation in which these points, as well as others directly concerned with biological transport, have been ill considered. My contribution to this book might best be thought of as a list of topics to be considered before embarking on an investigation requiring solute translocation across a biological membrane. These topics, as well as the important one of regulation of transmembrane flow by hormones and other effectors, represent a reasonably complete view of solute translocation in biological systems. To the novice, many of these considerations might seem hopelessly complex. The committed student of transport, however, will already know the enticement of the translocation event and the many remarkable ways in which soluble molecules of all kinds move from one place to another in the complex organism.
In Vitro to In Vivo Extrapolation of Metabolic Rate Constants for Physiologically Based Pharmacokinetic Models
Published in John C. Lipscomb, Edward V. Ohanian, Toxicokinetics and Risk Assessment, 2016
Some enzymes are membrane bound to cellular organelles, such as the endoplasmic reticulum or mitochondria, while others are present in the soluble portion of the cell known as the cytoplasm. However, the aqueous cytoplasm of the cell is highly organized via a group of polymeric proteins called the cytomatrix, and soluble enzymes appear to be associated with this dynamic network (3–5). This intracellular organization can influence the efficiency of enzyme catalysis and promote the coupling of metabolic processes. For example, a chemical that is hydroxylated by endoplasmic reticulum-bound cytochrome P450 (CYP) can be so efficiently conjugated with glucuronic acid by neighboring membrane-bound glucuronosyl transferase that the free alcohol product cannot be detected in the cell. The coupling of metabolic processes can lead to very efficient detoxication of toxicants, but it can also promote toxication processes that can ultimately lead to cellular damage and death.
Production, purification and biochemical characterisation of a novel lipase from a newly identified lipolytic bacterium Staphylococcus caprae NCU S6
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2021
Junxin Zhao, Maomao Ma, Zheling Zeng, Ping Yu, Deming Gong, Shuguang Deng
Temperature is one of the most important factors affecting the reaction rate of enzyme catalysis. As shown in Figure 5(A), the lipase was active in the wide range of temperatures from 10 to 60 °C. The maximum hydrolytic activity was found at 40 °C, with the relative activity and specific activity of 100% and 503 U/mg respectively. The optimal reaction temperature was lower than the lipase from Aureobasidium pullulans (55 °C)18. Activity analyses of the lipase at temperatures from 10 to 60 °C for 240 min showed that the remaining activity at 40 °C was at the highest level (Figure 5(B)). Only the extremely high temperatures, such as 50 or 60 °C, significantly inhibited the lipase activity, and prolonged incubation may rapidly inactivate the lipase. The highest remaining activity was at 40 °C for 80 min, and the lipase activity decreased with an increase of culture period. The decrease may be because the molecular structure of the enzyme was irreversibly changed, which may have altered the configuration of the active site, thereby decreasing interaction of the lipase with substrates19.
Recent advances in the development of polyethylenimine-based gene vectors for safe and efficient gene delivery
Published in Expert Opinion on Drug Delivery, 2019
Cuiping Jiang, Jiatong Chen, Zhuoting Li, Zitong Wang, Wenli Zhang, Jianping Liu
As the substances that are inherently present in the human body, biological molecules draw growing interests as promising triggering motifs in the design of smart PEI-based gene vectors. Among different classes of biological components, ATP, enzyme, glucose, and antigen are the most attractive endogenous stimuli that enable biomolecule-responsive release. As we all know, enzymes are potent catalysts during almost all biological processes, and enzyme catalysis is highly selective towards specific substrates under mild conditions. Using tumor as an example again, several enzymes (i.e. proteases, lipase, hyaluronidase (HAase), etc.) have great potential to be specific stimuli in a controlled gene delivery system [117]. For instance, Yin et al. [118] reported an HA-conjugated PEI polymer for the active tumor targeting via interaction of HA with CD44 receptor. Once the nanocarrier reached the tumor extracellular matrix, the surface layer of HA would be deshielded under the catalysis of HAase, leading to the enhanced cellular uptake owing to the exposure of positive charges.
The prodrug approach in the era of drug design
Published in Expert Opinion on Drug Delivery, 2019
While current trends point toward an age of biological treatments such as antibodies, prodrugs still prove viable products. I believe that the prodrug approach has a strong potential to grow rapidly in such a way that it will provide more than 25% of the marketed therapeutics during the coming decade if the researchers in the field utilize the computational methods used in the drug design and discovery. Computational methods based on quantum mechanics and MM could be used for the design of prodrugs. Prodrugs targeting transporters could be designed with the assistance of computational methods such as docking and etc. In a similar way, prodrugs targeting esterases, amidases and, etc., can be more effective if their design is relied on DFT and ab-inito methods that they have a great ability to predict kinetics of chemical systems. In our group we have used DFT methods for unraveling mechanisms of intramolecular processes that were previously studied in the labs of others to comprehend enzyme catalysis. Our goal was to establish a correlation between experimental and calculated kinetic values and to use the resulting correlation’s equation for the design of a number of novel prodrugs [17].