Metabolic Generation and Utilization of Phosphate Bond Energy
22 Nov 2006-pp 99-162
About: The article was published on 2006-11-22. It has received 269 citations till now. The article focuses on the topics: Phosphate & Bond energy.
TL;DR: This article corrects the article on p. 100 in vol.
Abstract: [This corrects the article on p. 100 in vol. 41.].
TL;DR: The theoretical bases of indirect calorimetry are reviewed in a detailed and orderly fashion and special cases, such as the occurrence of net lipid synthesis or gluconeogenesis, are formally considered with derivation of explicit stoichiometric equations.
Abstract: Indirect calorimetry is the method by which the type and rate of substrate utilization, and energy metabolism are estimated in vivo starting from gas exchange measurements. This technique provides unique information, is noninvasive, and can be advantageously combined with other experimental methods to investigate numerous aspects of nutrient assimilation, thermogenesis, the energetics of physical exercise, and the pathogenesis of metabolic diseases. Since its use as a research tool in metabolism is growing, the theoretical bases of indirect calorimetry are here reviewed in a detailed and orderly fashion. Special cases, such as the occurrence of net lipid synthesis or gluconeogenesis, are formally considered with derivation of explicit stoichiometric equations. The limitations of indirect calorimetry, both theoretical and technical, are discussed in the context of circumstances of clinical interest in metabolism.
TL;DR: Evidence is presented that nucleoid proteins orchestrate a progression of distinct nucleoprotein complexes to ensure proper transcription of its gene and that acetyl∼P influences cellular processes from organelle biogenesis to cell cycle regulation and from biofilm development to pathogenesis.
Abstract: To succeed, many cells must alternate between life-styles that permit rapid growth in the presence of abundant nutrients and ones that enhance survival in the absence of those nutrients. One such change in life-style, the “acetate switch,” occurs as cells deplete their environment of acetate-producing carbon sources and begin to rely on their ability to scavenge for acetate. This review explains why, when, and how cells excrete or dissimilate acetate. The central components of the “switch” (phosphotransacetylase [PTA], acetate kinase [ACK], and AMP-forming acetyl coenzyme A synthetase [AMP-ACS]) and the behavior of cells that lack these components are introduced. Acetyl phosphate (acetyl∼P), the high-energy intermediate of acetate dissimilation, is discussed, and conditions that influence its intracellular concentration are described. Evidence is provided that acetyl∼P influences cellular processes from organelle biogenesis to cell cycle regulation and from biofilm development to pathogenesis. The merits of each mechanism proposed to explain the interaction of acetyl∼P with two-component signal transduction pathways are addressed. A short list of enzymes that generate acetyl∼P by PTA-ACKA-independent mechanisms is introduced and discussed briefly. Attention is then directed to the mechanisms used by cells to “flip the switch,” the induction and activation of the acetate-scavenging AMP-ACS. First, evidence is presented that nucleoid proteins orchestrate a progression of distinct nucleoprotein complexes to ensure proper transcription of its gene. Next, the way in which cells regulate AMP-ACS activity through reversible acetylation is described. Finally, the “acetate switch” as it exists in selected eubacteria, archaea, and eukaryotes, including humans, is described.
Cites background from "Metabolic Generation and Utilizatio..."
...Acetyl P is a high-energy form of phosphate (271)....
TL;DR: Recent work indicated that bacteria can also use futile cycles of potassium, ammonia, and protons through the cell membrane to dissipate ATP either directly or indirectly, and the utility of energy spilling in bacteria has been a curiosity.
Abstract: Biomass formation represents one of the most basic aspects of bacterial metabolism. While there is an abundance of information concerning individual reactions that result in cell duplication, there has been surprisingly little information on the bioenergetics of growth. For many years, it was assumed that biomass production (anabolism) was proportional to the amount of ATP which could be derived from energy-yielding pathways (catabolism), but later work showed that the ATP yield (YATP) was not necessarily a constant. Continuous-culture experiments indicated that bacteria utilized ATP for metabolic reactions that were not directly related to growth (maintenance functions). Mathematical derivations showed that maintenance energy appeared to be a growth rate-independent function of the cell mass and time. Later work, however, showed that maintenance energy alone could not account for all the variations in yield. Because only some of the discrepancy could be explained by the secretion of metabolites (overflow metabolism) or the diversion of catabolism to metabolic pathways which produced less ATP, it appeared that energy-excess cultures had mechanisms of spilling energy. Bacteria have the potential to spill excess ATP in futile enzyme cycles, but there has been little proof that such cycles are significant. Recent work indicated that bacteria can also use futile cycles of potassium, ammonia, and protons through the cell membrane to dissipate ATP either directly or indirectly. The utility of energy spilling in bacteria has been a curiosity. The deprivation of energy from potential competitors is at best a teleological explanation that cannot be easily supported by standard theories of natural selection. The priming of intracellular intermediates for future growth or protection of cells from potentially toxic end products (e.g., methylglyoxal) seems a more plausible explanation.
TL;DR: It was proposed in 1951 that contracting muscle fibers liberate creatine, which acts to produce an acceptor effect--later called respiratory control--on the muscle mitochondria, which established a molecular basis for a phosphorylcreatine-creatine shuttle for energy transport in heart and skeletal muscle.
Abstract: In order to explain the insulin-like effect of exercise, it was proposed in 1951 that contracting muscle fibers liberate creatine, which acts to produce an acceptor effect--later called respiratory control--on the muscle mitochondria. The development of this notion paralleled the controversy between biochemists and physiologists over the delivery of energy for muscle contraction. With the demonstration of functional compartmentation of creatine kinase on the mitochondrion, it became clear that the actual form of energy transport in the muscle fiber is phosphorylcreatine. The finding of an isoenzyme of creatine phosphokinase attached to the M-line region of the myofibril revealed the peripheral receptor for the mitochondrially generated phosphorylcreatine. This established a molecular basis for a phosphorylcreatine-creatine shuttle for energy transport in heart and skeletal muscle and provided an explanation for the inability to demonstrate experimentally a direct relation between muscle activity and the concentrations of adenosine triphosphate and adenosine diphosphate.
TL;DR: Preliminary experiments have shown that phosphatase is not destroyed either by alcohol or by exposure to 56°C in completely dehydrated state, and a useable technic has been worked out on the basis of this principle.
Abstract: In preliminary experiments the phosphatase activity of aqueous extracts of dog kidney cortex made (a) of fresh ground tissue, (b) of ground tissue dehydrated with several changes of 95% and absolute alcohol, (c) of dehydrated ground tissue exposed to 56°C for one hour was determined by the Berenblum-Chain1 modification of Kay's2 method. These experiments have shown that phosphatase is not destroyed either by alcohol or by exposure to 56°C in completely dehydrated state, the maximum decrease in activity observed having amounted to less than 20%. Moreover, purification of phosphatase by alcohol precipitation has been successfully used by Mart-land and Robison.3 It appeared possible to demonstrate phosphatase in celloidin or paraffin sections on the basis of the following principle: If tissue sections containing active phosphatase are incubated with a solution of sodium glycerophosphate or of some other suitable ester-phosphate, such as hexose-phosphate or nucleinate, at a suitable pH, at the sites where pho...