Extracellular Inorganic Phosphate-Induced Release of Reactive Oxygen Species: Roles in Physiological Processes and Disease Development

Inorganic phosphate (Pi) is an essential nutrient for living organisms and is maintained in equilibrium in the range of 0.8–1.4 mM Pi. Pi is a source of organic constituents for DNA, RNA, and phospholipids and is essential for ATP formation mainly through energy metabolism or cellular signalling modulators. In mitochondria isolated from the brain, liver, and heart, Pi has been shown to induce mitochondrial reactive oxygen species (ROS) release. Therefore, the purpose of this review article was to gather relevant experimental records of the production of Pi-induced reactive species, mainly ROS, to examine their essential roles in physiological processes, such as the development of bone and cartilage and the development of diseases, such as cardiovascular disease, diabetes, muscle atrophy, and male reproductive system impairment. Interestingly, in the presence of different antioxidants or inhibitors of cytoplasmic and mitochondrial Pi transporters, Pi-induced ROS production can be reversed and may be a possible pharmacological target.

Electron transfer complexes in the gut dictate high abundance circulating metabolites

It has long been thought that Clostridium and its relatives couple the oxidation of one substrate to the reduction of another, yielding energy in the former step and re-achieving redox balance with the latter. By probing the genetics of reductive metabolic pathways in the gut resident C. sporogenes, we find unexpectedly that electron transfer complexes are required for the production of reduced metabolites. Physiologic measurements in vitro indicate that the reductive pathways are coupled to ATP formation, revealing that energy is captured not just during substrate oxidation, but also during coupled reduction, accounting for ~40% of the ATP generated in the cell. Electron transfer complex mutants are attenuated for growth in the mouse gut, demonstrating the importance of energy capture during reductive metabolism for gut colonization. Our findings revise a long-standing model for energy capture by Clostridium sp., and they reveal that the production of high-abundance molecules by a commensal bacterium within the host gut is linked to an energy yielding redox process.

Important Role of Mitochondria and the Effect of Mood Stabilizers on Mitochondrial Function

Mitochondria primarily serve as source of cellular energy through the Krebs cycle and β-oxidation to generate substrates for oxidative phosphorylation. Redox reactions are used to transfer electrons through a gradient to their final acceptor, oxygen, and to pump hydrogen protons into the intermembrane space. Then, ATP synthase uses the electrochemical gradient to generate adenosine triphosphate (ATP). During these processes, reactive oxygen species (ROS) are generated. ROS are highly reactive molecules with important physiological functions in cellular signaling. Mitochondria play a crucial role in intracellular calcium homeostasis and serve as transient calcium stores. High levels of both, ROS and free cytosolic calcium, can damage mitochondrial and cellular structures and trigger apoptosis. Impaired mitochondrial function has been described in many psychiatric diseases, including mood disorders, in terms of lowered mitochondrial membrane potential, suppressed ATP formation, imbalanced Ca2+ levels and increased ROS levels. In vitro models have indicated that mood stabilizers affect mitochondrial respiratory chain complexes, ROS production, ATP formation, Ca2+ buffering and the antioxidant system. Most studies support the hypothesis that mitochondrial dysfunction is a primary feature of mood disorders. The precise mechanism of action of mood stabilizers remains unknown, but new mitochondrial targets have been proposed for use as mood stabilizers and mitochondrial biomarkers in the evaluation of therapy effectiveness.

Pyrophosphate-Dependent ATP Formation from Acetyl Coenzyme A inSyntrophus aciditrophicus, a New Twist on ATP Formation

ABSTRACTSyntrophus aciditrophicusis a model syntrophic bacterium that degrades key intermediates in anaerobic decomposition, such as benzoate, cyclohexane-1-carboxylate, and certain fatty acids, to acetate when grown with hydrogen-/formate-consuming microorganisms. ATP formation coupled to acetate production is the main source for energy conservation byS. aciditrophicus. However, the absence of homologs for phosphate acetyltransferase and acetate kinase in the genome ofS. aciditrophicusleaves it unclear as to how ATP is formed, as most fermentative bacteria rely on these two enzymes to synthesize ATP from acetyl coenzyme A (CoA) and phosphate. Here, we combine transcriptomic, proteomic, metabolite, and enzymatic approaches to show thatS. aciditrophicususes AMP-forming, acetyl-CoA synthetase (Acs1) for ATP synthesis from acetyl-CoA.acs1mRNA and Acs1 were abundant in transcriptomes and proteomes, respectively, ofS. aciditrophicusgrown in pure culture and coculture. Cell extracts ofS. aciditrophicushad low or undetectable acetate kinase and phosphate acetyltransferase activities but had high acetyl-CoA synthetase activity under all growth conditions tested. Both Acs1 purified fromS. aciditrophicusand recombinantly produced Acs1 catalyzed ATP and acetate formation from acetyl-CoA, AMP, and pyrophosphate. High pyrophosphate levels and a high AMP-to-ATP ratio (5.9 ± 1.4) inS. aciditrophicuscells support the operation of Acs1 in the acetate-forming direction. Thus,S. aciditrophicushas a unique approach to conserve energy involving pyrophosphate, AMP, acetyl-CoA, and an AMP-forming, acetyl-CoA synthetase.IMPORTANCEBacteria use two enzymes, phosphate acetyltransferase and acetate kinase, to make ATP from acetyl-CoA, while acetate-forming archaea use a single enzyme, an ADP-forming, acetyl-CoA synthetase, to synthesize ATP and acetate from acetyl-CoA.Syntrophus aciditrophicusapparently relies on a different approach to conserve energy during acetyl-CoA metabolism, as its genome does not have homologs to the genes for phosphate acetyltransferase and acetate kinase. Here, we show thatS. aciditrophicususes an alternative approach, an AMP-forming, acetyl-CoA synthetase, to make ATP from acetyl-CoA. AMP-forming, acetyl-CoA synthetases were previously thought to function only in the activation of acetate to acetyl-CoA.

KREBER`S ADVENTURES: COMPUTER GAME ABOUT THE ATP FORMATION

Introduction: Biochemistry, as well as other subjects related to molecular area, have several abstract and difficult concepts to be understood, therefore, many educational innovations have been developed, highlighting the digital games. The digital games feature a playful and motivational character that encourages students during the concepts learning, with a different way to learning the concepts studied. Objectives: The objective of this study was the development of a computer game focused on the concepts of ATP formation, including the glycolytic pathway, Krebs cycle and Electron Transport Chain, as well as aspects related to the regulation, and evaluate the usability of it, as well as some evidence of its educational potential. Material and methods: The development of the game followed the following steps: definition of the subject; understanding of game developer (it was chosen the GameMaker); storyboard creation of the game; prototyping, implementation and usability testing. For the evaluation, inspection usability was performed (without involving end users) and subsequently the cognitive route and the usability questionnaire (the latter two with students of the discipline of Biochemistry). Results: The game approached the energy metabolism in three phases: the glycolytic pathway, Krebs cycle and electron transport chain. Each phase has a different purpose, with some questions about the ways. To complete the game, you must correctly answer the questions, avoid the obstacles and achieve the goals of each phase. After usability testing, it found that users could, in a playful manner, actively interact with the content addressed and, through the difficulties presented in the game, had the opportunity to expand and review their knowledge. Conclusions: The game was identified as a motivating and innovative proposal for teaching, and it had good usability for undergraduate students. The ludic worked as a pedagogical practice encourages student for learning and may assist in the construction of knowledge.

Human prostasomes express glycolytic enzymes with capacity for ATP production

Prostasomes are prostate-derived, exosome-like microvesicles that transmit signaling complexes between the acinar epithelial cells of the prostate and sperm cells. The vast majority of prostasomes have a diameter of 30–200 nm, and they are generally surrounded by a classical membrane bilayer. Using a selected proteomic approach, it became increasingly clear that prostasomes harbor distinct subsets of proteins that may be linked to adenosine triphosphate (ATP) metabolic turnover that in turn might be of importance in the role of prostasomes as auxiliary instruments in the fertilization process. Among the 21 proteins identified, most of the enzymes of anaerobic glycolysis were represented, and three of the glycolytic enzymes present are among the top 10 proteins found in most exosomes, once again linking prostasomes to the exosome family. Other prostasomal enzymes involved in ATP turnover were adenylate kinase, ATPase, 5′-nucleotidase, and hexose transporters. The identified enzymes in their prostasomal context were operational for ATP formation when supplied with substrates. The net ATP production was low due to a high prostasomal ATPase activity that could be partially inhibited by vanadate that was utilized to profile the ATP-forming ability of prostasomes. Glucose and fructose were equivalent as glycolytic substrates for prostasomal ATP formation, and the enzymes involved were apparently surface located on prostasomes, since an alternative substrate not being membrane permeable (glyceraldehyde 3-phosphate) was operative, too. There is no clear-cut function linked to this subset of prostasomal proteins, but some possible roles are discussed.