Form Of Adenosine Triphosphate Research Articles

Role and Function of Mitochondria

Mitochondrial diseases are a group of disorders caused by pathologic dysfunction of the mitochondrial respiratory chain. They present with a wide range of clinical expression. Although neurologic impairment is a common manifestation but they can affect other systems, either exclusively or in combination. Mitochondria are intracellular organelles found in almost all human cells. They are responsible for aerobic metabolism through oxidative phosphorylation, which leads to energy production in the form of adenosine triphosphate (ATP). Each human cell contains on average hundreds to thousands of mitochondria. The exception is mature red blood cells, which rely exclusively on anaerobic metabolism and contain no mitochondria. Mitochondria have four main compartments: 1. The outer membrane, 2.The intermembranous space, 3.The inner membrane, 4.The matrix. In addition to ATP generation through the respiratory chain, mitochondria perform multiple other metabolic functions, including pyruvate oxidation, the Krebs cycle, fatty acid oxidation, and amino acid metabolism. All of these tasks take place in the matrix. Although any abnormality in the above pathways could be technically designated as a mitochondrial disorder, only defects in the respiratory chain are traditionally referred to as primary mitochondrial diseases. The respiratory chain is composed of five enzyme complexes (complex I, II, III, IV, V) that are involved in receipt and transfer of electrons through these compartments .Oxidative phosphorylation takes place along the inner mitochondrial membrane, which contains the respiratory chain proteins. Mitochondria are under the dual control of mitochondrial DNA and nuclear DNA. Mitochondrial DNA has several characteristics that distinguish them from their nuclear counterparts. These include: Maternal inheritance, heteroplasmy (e.g. some pathologic DNA copy, mitochondria or cells mixed with healthy ones), threshold effect (A minimal number of mutated cells needed before respiratory chain and cellular dysfunction occur), Mitotic segregation (e.g. since organelles are randomly distributed at the time of cell division, a change in the amount of mutant DNA in a cell occurs and surpass its threshold, therefore clinical phenotype can be changed in a previously unaffected tissue). Post mitotic replication (Mitochondrial DNA replication is not linked to the cell cycle. This allows for post mitotic mitochondrial DNA replication in terminally differentiated cells such as neurons or muscle in response to specific stimuli (exercise, increased metabolic demand). This explains how the symptomatic threshold can be exceeded later in life in previously asymptomatic tissues). In contrast to mitochondrial DNA, nuclear DNA mutations affecting the mitochondria follow Mendelian genetics. Most of the nuclear genes that are Gholamreza ZAMANI MD

Highlight: On the Origin of the Sexes

Highlight: On the Origin of the Sexes

Fine-tuning Metabolic Switches

Fine-tuning Metabolic Switches

Measuring interference of drug-like molecules with the respiratory chain: toward the early identification of mitochondrial uncouplers in lead finding.

The electron transport chain (ETC) couples electron transfer between donors and acceptors with proton transport across the inner mitochondrial membrane. The resulting electrochemical proton gradient is used to generate chemical energy in the form of adenosine triphosphate (ATP). Proton transfer is based on the activity of complex I-V proteins in the ETC. The overall electrical activity of these proteins can be measured by proton transfer using Solid Supported Membrane technology. We tested the activity of complexes I, III, and V in a combined assay, called oxidative phosphorylation assay (oxphos assay), by activating each complex with the corresponding substrate. The oxphos assay was used to test in-house substances from different projects and several drugs currently available on the market that have reported effects on mitochondrial functions. The resulting data were compared to the influence of the respective compounds on mitochondria as determined by oxygen consumption and to data generated with an ATP depletion assay. The comparison shows that the oxidative phosphorylation assay provides both a rapid approach for detecting interaction of compounds with respiratory chain proteins and information on their mode of interaction. Therefore, the oxphos assay is a useful tool to support structure activity relationship studies by allowing early identification of mitotoxicity and for analyzing the outcome of phenotypic screens that are susceptible to the generation of mitotoxicity-related artifacts.

Prostasomes from four different species are able to produce extracellular adenosine triphosphate (ATP)

BackgroundProstasomes are extracellular vesicles. Intracellularly they are enclosed by another larger vesicle, a so called “storage vesicle” equivalent to a multivesicular body of late endosomal origin. Prostasomes in their extracellular context are thought to play a crucial role in fertilization. MethodsProstasomes were purified according to a well worked-out schedule from seminal plasmas obtained from human, canine, equine and bovine species. The various prostasomes were subjected to SDS-PAGE separation and protein banding patterns were compared. To gain knowledge of the prostasomal protein systems pertaining to prostasomes of four different species proteins were analyzed using a proteomic approach. An in vitro assay was employed to demonstrate ATP formation by prostasomes of different species. ResultsThe SDS-PAGE banding pattern of prostasomes from the four species revealed a richly faceted picture with most protein bands within the molecular weight range of 10–150kDa. Some protein bands seemed to be concordant among species although differently expressed and the number of protein bands of dog prostasomes seemed to be distinctly fewer. Special emphasis was put on proteins involved in energy metabolic turnover. Prostasomes from all four species were able to form extracellular adenosine triphosphate (ATP). ATP formation was balanced by ATPase activity linked to the four types of prostasomes. ConclusionThese potencies of a possession of functional ATP-forming enzymes by different prostasome types should be regarded against the knowledge of ATP having a profound effect on cell responses and now explicitly on the success of the sperm cell to fertilize the ovum. General significanceThis study unravels energy metabolic relationships of prostasomes from four different species.

Abiotic Photophosphorylation Model Based on Abiogenic Flavin and Pteridine Pigments

A model for abiotic photophosphorylation of adenosine diphosphate by orthophosphate with the formation of adenosine triphosphate was studied. The model was based on the photochemical activity of the abiogenic conjugates of pigments with the polymeric material formed after thermolysis of amino acid mixtures. The pigments formed showed different fluorescence parameters depending on the composition of the mixture of amino acid precursors. Thermolysis of the mixture of glutamic acid, glycine, and lysine (8:3:1) resulted in a predominant formation of a pigment fraction which had the fluorescence maximum at 525 nm and the excitation band maxima at 260, 375, and 450 nm and was identified as flavin. When glycine in the initial mixture was replaced with alanine, a product formed whose fluorescence parameters were typical to pteridines (excitation maximum at 350 nm, emission maximum at 440 nm). When irradiated with the quasi-monochromatic light (over the range 325-525 nm), microspheres in which flavin pigments were prevailing showed a maximum photophosphorylating activity at 375 and 450 nm, and pteridine-containing chromoproteinoid microspheres were most active at 350 nm. The positions and the relative height of maxima in the action spectra correlate with those in the excitation spectra of the pigments, which point to the involvement of abiogenic flavins and pteridines in photophosphorylation.

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.

Anesthesia Literature Review

Anesthesia Literature Review

Inhibition of Maltase‐Glucoamylase Activity to Hydrolyze α‐1,4 Linkages by the Presence of Undigested Sucrose

Inhibition of Maltase‐Glucoamylase Activity to Hydrolyze α‐1,4 Linkages by the Presence of Undigested Sucrose

Oncogenic K-ras expression is associated with derangement of the cAMP/PKA pathway and forskolin-reversible alterations of mitochondrial dynamics and respiration

The Warburg effect in cancer cells has been proposed to involve several mechanisms, including adaptation to hypoxia, oncogenes activation or loss of oncosuppressors and impaired mitochondrial function. In previous papers, it has been shown that K-ras transformed mouse cells are much more sensitive as compared with normal cells to glucose withdrawal (undergoing apoptosis) and present a high glycolytic rate and a strong reduction of mitochondrial complex I. Recent observations suggest that transformed cells have a derangement in the cyclic adenosine monophosphate/cAMP-dependent protein kinase (cAMP/PKA) pathway, which is known to regulate several mitochondrial functions. Herein, the derangement of the cAMP/PKA pathway and its impact on transformation-linked changes of mitochondrial functions is investigated. Exogenous stimulation of PKA activity, achieved by forskolin treatment, protected K-ras-transformed cells from apoptosis induced by glucose deprivation, enhanced complex I activity, intracellular adenosine triphosphate (ATP) levels, mitochondrial fusion and decreased intracellular reactive oxygen species (ROS) levels. Several of these effects were almost completely prevented by inhibiting the PKA activity. Short-time treatment with compounds favoring mitochondrial fusion strongly decreased the cellular ROS levels especially in transformed cells. These findings support the notion that glucose shortage-induced apoptosis, specific of K-ras-transformed cells, is associated to a derangement of PKA signaling that leads to mitochondrial complex I decrease, reduction of ATP formation, prevalence of mitochondrial fission over fusion, and thereby opening new approaches for development of anticancer drugs.

Three-color Förster resonance energy transfer within single F[sub O]F[sub 1]-ATP synthases: monitoring elastic deformations of the rotary double motor in real time

Catalytic activities of enzymes are associated with elastic conformational changes of the protein backbone. Förster-type resonance energy transfer, commonly referred to as FRET, is required in order to observe the dynamics of relative movements within the protein. Förster-type resonance energy transfer between two specifically attached fluorophores provides a ruler with subnanometer resolution between 3 and 8 nm, submillisecond time resolution for time trajectories of conformational changes, and single-molecule sensitivity to overcome the need for synchronization of various conformations. F(O)F(1)-ATP synthase is a rotary molecular machine which catalyzes the formation of adenosine triphosphate (ATP). The Escherichia coli enzyme comprises a proton driven 10 stepped rotary F(O) motor connected to a 3-stepped F(1) motor, where ATP is synthesized. This mismatch of step sizes will result in elastic deformations within the rotor parts. We present a new single-molecule FRET approach to observe both rotary motors simultaneously in a single F(O)F(1)-ATP synthase at work. We labeled this enzyme with three fluorophores, specifically at the stator part and at the two rotors. Duty cycle-optimized with alternating laser excitation, referred to as DCO-ALEX, allowed to control enzyme activity and to unravel associated transient twisting within the rotors of a single enzyme during ATP hydrolysis and ATP synthesis. Monte Carlo simulations revealed that the rotor twisting is larger than 36 deg.

Bacterial Chimeras and Reversible Phosphorylation: The Work of Walther Stoeckenius

In 1971, Walther Stoeckenius discovered that Halobacterium halobium contains a purple pigment that is chemically similar to rhodopsin and works as a light-driven proton pump. This discovery set Stoeckenius on a research path centered on bacteriorhodopsin, which included the creation of a bovine-soybean-halobacteria chimera that was able to produce ATP when exposed to light and the discovery of a class of proteins that are phosphorylated in a light-dependent manner.

Nitazoxanide in the treatment of chronic cutaneous leishmaniasis resistant to traditional sodium stibogluconate

Nitazoxanide in the treatment of chronic cutaneous leishmaniasis resistant to traditional sodium stibogluconate

Bioenergetic Analysis of FLAG Tagged-Subunit 8 of Saccharomyces cerevisiae Mitochondrial ATP Synthase

The majority of cellular energy in the form of adenosine triphosphate (ATP) is synthesized by the F1F0-ATP synthase.  The yeast mitochondrial F1F0-ATP synthase is a multisubunit complex that contains at least 17 different subunits grouped into F1 and F0 sectors.  Subunit 8 of yeast mitochondrial ATP synthase is a hydrophobic protein of 48 amino acids encoded by the mitochondrial ATP8 gene.  Subunit 8 has three distinct domains; an N-terminal domain, a central hydrophobic domain and a C-terminal domain.  FLAG tag addition to the C-terminus of subunit 8 and its variants has facilitated elucidation of subunit 8's membrane topology.  In order to analyze its detailed structure and function, a set of strains expressing FLAG tagged-subunit 8 and its variants were subjected to bioenergetic analysis at cellular and mitochondrial levels.   Results obtained showed that the hydrophobic character of the central hydrophobic domain of subunit 8 is essential for functional coupling between F1 and F0 sectors, hence for mitochondrial ATP synthase function.

Structural and electronic features of the ubiquinone and ubiquinol molecules: molecular dynamics and quantum chemical treatments

The coenzyme Q (CoQ) molecule plays a critical role in the biochemical generation of energy in the form of adenosine triphosphate. Various types of CoQ can be classified according to their number of isoprenoid units in the tail. In human beings, CoQ10 is produced and is necessary for the basic functioning of cells. CoQ10 exists in two forms, as ubiquinone (UQ) and as ubiquinol (UQH2), which have different roles in the body. Molecular dynamics (MD) simulations for the analysis of the effects of solvents on the structure of the UQ molecule are presented. Besides, semi-empirical molecular orbital PM3 calculation is applied to obtain structural and electronic properties of both the UQ and the UQH2 molecules. According to the MD simulation, the UQ molecule seems to be flexible both in vacuum and in water. On the other hand, the molecule stays more rigid in methanol. PM3 calculations show that both molecules are quite hydrophobic. Furthermore, UQ is chemically more reactive than UQH2, but the latter is kinetically more stable than the former.

Mitochondria in heart failure

This review focuses on the evidence accumulated in humans and animal models to the effect that mitochondria are key players in the progression of heart failure (HF). Mitochondria are the primary source of energy in the form of adenosine triphosphate that fuels the contractile apparatus, and are thus essential for the pumping activity of the heart. We evaluate changes in mitochondrial morphology and alterations in the main components of mitochondrial energetics, such as substrate utilization and oxidative phosphorylation coupled with the level of respirasomes, in the context of their contribution to the chronic energy deficit and mechanical dysfunction in HF.

Mitochondrial metabolism and diabetes.

The oversupply of calories and sedentary lifestyle has resulted in a rapid increase of diabetes prevalence worldwide. During the past two decades, lines of evidence suggest that mitochondrial dysfunction plays a key role in the pathophysiology of diabetes. Mitochondria are vital to most of the eukaryotic cells as they provide energy in the form of adenosine triphosphate by oxidative phosphorylation. In addition, mitochondrial function is an integral part of glucose-stimulated insulin secretion in pancreatic β-cells. In the present article, we will briefly review the major functions of mitochondria in regard to energy metabolism, and discuss the genetic and environmental factors causing mitochondrial dysfunction in diabetes. In addition, the pathophysiological role of mitochondrial dysfunction in insulin resistance and β-cell dysfunction are discussed. We argue that mitochondrial dysfunction could be the central defect causing the abnormal glucose metabolism in the diabetic state. A deeper understanding of the role of mitochondria in diabetes will provide us with novel insights in the pathophysiology of diabetes. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00047.x, 2010).

Abstract 4654: Mitochondrial variants and clinical outcome of oral squamous cell carcinoma in Taiwan

Abstract Mitochondria are essential cytoplasmic organelles, generating cellular energy in the form of adenosine triphosphate by oxidative phosphorylation. A large volume of studies have indicated that polymorphisms in the mitochondrial genome are associated with risk of various diseases, including cancer. However, only few studies examined the effect of polymorphisms on cancer outcome. To explore the possible role of mitochondrial polymorphisms on clinical outcome of oral squamous cell carcinomas (OSCCs) in Taiwan, 7 common length polymorphism (mtLP) sites and the control D-loop region of mitochondrial genome were genotyped or screened by DNA direct sequencing in 298 OSCCs. One hundred and seventy-eight single-nucleotide polymorphisms (SNPs) were found in the D-loop region and 19 SNPs were presented with a high frequency (> 10%) of variant form. The frequency of variant form in the mtLP sites were quite various ranging from 3.7% to 62.8%. In total, 7 variants from 6 polymorphism sites (2 mtLPs and 4 SNPs) were associated with overall survival. Four subgroups (clusters 1 - 4) were identified by hierarchical clustering of the OSCCs based on the genotypes of these 6 polymorphism sites. We found that the overall survival was significantly different among these 4 OSCC clusters. An index score designated as the total effects of the genotypes of these 6 polymorphism sites on survival for each individual was also developed using the estimates from the Cox model. We found that individual with the higher the index score had the poorer disease-free and overall survival. In summary, the findings provide the first evidence pointing toward mitochondrial variants affect the clinical outcome in OSCC and the underlying mechanisms are worthy to investigate. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4654.

Ischaemic preconditioning is related to decreasing levels of extracellular adenosine that may be metabolically useful in the at‐risk myocardium: an experimental study in the pig

'Pre-treatment' with short repetitive periods of ischaemia (ischaemic preconditioning) has proved to be a powerful mechanism for modification of the extent of myocardial damage following acute coronary artery occlusion. The exact mechanism of protection induced by ischaemic preconditioning is not known. We herewith put forward a contributing component for protection with preconditioning involving a shift in the adenylate kinase (AK) equilibrium reaction in favour of adenosine triphosphate (ATP) formation. A coronary artery was occluded in anaesthetized thoracotomized pigs to induce ischaemic preconditioning as well as a longer period of ischaemia. Microdialysis probes were inserted in ischaemic and control myocardium and were infused with (14)C- adenosine with two different specific activities. (14)C-lactate was identified and measured in the effluent. (14)C-adenosine was taken up by non-preconditioned and preconditioned myocardium during ischaemia. Significantly increased levels of (14)C-lactate were recovered in preconditioned myocardium. (14)C-adenosine with high specific activity resulted in a specific activity of lactate that was 2.7 times higher than that of lactate after administration of (14)C-adenosine with low specific activity. Mass spectrography verified the identity of (14)C-lactate. Preconditioning up-regulates a new metabolic pathway (starting with 5'-nucleotidase and ending up with lactate) resulting in ATP formation in the micromolar range on top of another effect terminating in a useful shift in the AK equilibrium reaction in favour of ATP generation in the millimolar range. Although the up-regulation of the purine nucleoside phosphorylase pathway is clearly demonstrated, its biological relevance remains to be proved.

Lidocaine Enhances Apoptosis and Suppresses Mitochondrial Functions of Human Neutrophil In Vitro

Neutrophils play an essential role in innate immunity and against infection. Mitochondria are organelles that produce energy in the form of adenosine triphosphate (ATP), which is required for maintaining the function and structure of cells and organs. Although local anesthetics (LAs) are widely used in clinical practice, it remains unclear whether LAs such as lidocaine, ropivacaine, and bupivacaine affect neutrophil mitochondrial functions. The aim of this study was to examine whether LAs have any effects on human neutrophil mitochondrial functions. Freshly isolated human neutrophils were incubated with lidocaine, ropivacaine, or bupivacaine. The oxidative burst and phagocytic activity of neutrophils and apoptotic rate of neutrophils were measured to assess the effect of LAs on neutrophil functions. The ATP concentration, mitochondrial transmembrane potential (Deltapsim), and neutrophil mitochondrial morphology were also measured to evaluate the effect of LAs on mitochondrial functions. Lidocaine (400 microm) induced a reduction in the oxidative burst and phagocytosis activity of neutrophils by approximately 20%. The ATP concentration was significantly lower in lidocain-treated neutrophils compared with control neutrophils (876 +/- 25 vs. 1,332 +/- 76 pmol/10(6) neutrophils; p < 0.05). Mitochondrial transmembrane potential (Deltapsim) was also significantly lower in lidocaine-treated neutrophils compared with control neutrophils (p < 0.05). Lidocaine also induced mitochondrial structural changes and induced apoptosis of neutrophils. Ropivacaine and bupivacaine had no effect on neutrophil functions including mitochondrial function. Furthermore, the study of mitochondrial function depletion demonstrated that neutrophil function requires active mitochondrial function. Although ropivacaine and bupivacaine had no effect on neutrophil and mitochondrial functions, lidocaine suppressed neutrophil function, inhibited ATP synthesis, reduced mitochondrial membrane potential, and induced apoptosis.