Cells what is atp

ATP generation in heterotrophic cell factories. Fermentative glycolytic and respiratory generation of ATP may be compared to the front and rear axles, respectively, of four-wheel drive vehicles. Insight into symbiosis is important in considering the generation of intracellular ATP.

In eukaryotic cells, the respiratory chain resides in the mitochondrion. Mitochondrial microRNA target genes involved in energy metabolism and regulation of the ATP supply were recently identified in porcine muscle [ 11 ].

In contrast, Salvioli et al. Thus, developing cell factories with an artificially regulated ATP supply, according to a large demand for ATP, is a promising strategy to improve bioproduction yields Fig. However, the intracellular ATP supply of engineered cell factories would change because of an unnatural balance between ATP generation and consumption. Thus, improvements of the ATP supply are required to increase the production of target molecules, although it is difficult to measure the ATP supplying activity in the cell factories.

For example, one of the barriers that must be overcome to achieve economical biofuel production is the enhancement of the ATP supply to maintain metabolic homeostasis of engineered cells with a higher ATP demand due to metabolic genetic engineering [ 14 ]. Metabolic simulations indicate that the maintenance of the intracellular ATP supply is a key component required to improve cell factories together with coupling cell growth and metabolic production in anaerobic and aerobic fermentations [ 15 ].

Cell factories utilize carbon source to generate ATP by glycolysis and respiratory chain. Cell factories engineered in the pathways toward target product consume much more ATP for i sugar uptake, ii cell growth, iii biosynthesis and iv export of target products, and v tolerance to toxic compounds. Cell factories improve intracellular ATP supply to drive various cellular thermodynamically unfavorable reactions with keeping high ATP supply for better bioproductions.

ATP supply of the cell factories is enhanced by 1 addition of energy substrates, 2 control of pH condition, 3 metabolic engineering of pathways involved in ATP generation or ATP consumption and 4 enhancement of respiratory chain reaction.

The present review focuses on current developments in regulating the ATP supply used by various engineered cell factories for improving bioproduction yields to summarize their strategies for fundamental improvement of cell factories. Four strategies to regulate the ATP supply and future perspectives will be described in the following sections.

The strategies reviewed here improve resource uptake, cell growth, biosynthesis, export of target products, and tolerance to toxic compounds Fig. The intracellular ATP supply is strictly regulated by a carbon source that serves as the sole energy source for heterotrophic cell factories. For example, a yeast-cell factory uses carbon sources to supply ATP required for the production of glutathione [ 16 ]. Thus, the ATP supply is very low after depletion of the carbon supply. Direct addition of ATP is critical for enhancing ATP-consuming glutathione production in Candida utilis after glucose depletion [ 17 ].

These results demonstrate directly that the ATP supply is rate limiting for ATP-consuming production to continue after depletion of carbon sources. The addition of citric acid effectively increases the ATP supply. Addition of citric acid as an auxiliary energy substrate for dehydrogenase reactions by malic enzyme that generate NADH enhances the contribution of electrons from NADH, which pass through the electron transfer chain to generate a proton-motive force that enhances respiratory ATP synthesis via membrane-localized F o F 1 -ATP synthase [ 19 ].

Citric acid addition increases the cytosolic pH and decreases the vacuolar pH. Moreover, enhancing the ATP supply by up-regulating the expression of genes encoding citrate lyase, malate dehydrogenase, and malic enzyme, which are components of the citric acid pathway Fig. During the stationary phase of growth, enhanced pyruvic acid production increases the amount of acetic acid available to generate ATP through acetate kinase. Further, enhanced pyruvic acid production increases lactic acid biosynthesis through lactate dehydrogenase Fig.

Overall, the increase in the ATP supply due to enhanced ATP generation and reduced ATP consumption induced by the addition of citric acid increases cell growth and lactic acid production.

These studies show that the addition of energy-generating substrates such as ATP and citric acid is critical for increasing the intracellular ATP supply. The elevated ATP supply enhances cell growth, biosynthesis, and export of target products, and improves the acid tolerance of cell factories Fig.

However, using these compounds increases the total cost of industrial bioproduction. Controlling pH at acidic levels enhances the intracellular ATP supply in prokaryotic cell factories, because a lower external pH confers the advantage of generating a proton-motive force between the inner and outer surfaces of the cytoplasmic membrane, which drives F o F 1 -ATP synthase in the respiratory chain.

Further, an enhanced ATP supply is critical for stimulating the production of pullulan, which is a linear water-soluble extracellular homopolysaccharide of glucose [ 21 ].

The strong dependency of the molecular weight of pullulan on pH shows that the increased ATP supply enhances ATP-consuming pullulan biosynthesis and may increase pullulan excretion and acid tolerance [ 21 ]. Further, the intracellular ATP supply contributes to efficient ATP-consuming peptide production under acidic conditions [ 22 ]. For example, a high influx of lactic acid into a hybridoma cell line stimulates the tricarboxylic acid TCA cycle and maintains malate-aspartate flux at a level that induces a high rate of ATP generation and cell growth at low pH pH 6.

The synthesis of a variety of polymers such as polysaccharides, polynucleotides, polyorganic acids, and polypeptides requires large amounts of ATP. Acidic conditions enhance the intracellular ATP supply despite increases in ATP consumption required for acid uptake to maintain cellular homeostasis.

The optimal acidic conditions that exert the optimal balance between ATP generation and consumption are different in cell factories, depending on their acid tolerance. Conferring tolerance to acidic pH is a common area of interest of researchers engaged in bioproduction, because cell factories export various organic acids as byproducts. Thus, bioproduction is locked in a tradeoff between productivity and pH tolerance.

Deletion of the gene encoding non-ATP-generating acetic acid synthetic aldehyde dehydrogenase of Caldicellulosiruptor bescii , which grows efficiently on biomass without conventional pretreatment, enhances ATP-generating acetic acid synthesis and increases cell growth [ 25 ] Fig. Further, deletion of the gene encoding lactate dehydrogenase of C. Combinatorial deletion of genes encoding lactate dehydrogenase and aldehyde dehydrogenase decreases the levels of lactic acid and increases the levels of acetic acid [ 25 ].

The larger pool of ATP in this engineered C. In contrast, only 0. Milne et al. This engineered S. Heterologous overexpression of ATP-generating phosphoenolpyruvate carboxykinase Pck from Actinobacillus succinogenes in a mutant strain of Escherichia coli effectively enhances cell growth and succinic acid production [ 27 ] Fig.

Further, succinic acid production by Enterobacter aerogenes is enhanced using a similar strategy that increases ATP generation by heterogeneous overexpression of Pck together with deletion of the glucose phosphotransferase system [ 28 ].

Conversely, the ATP supply is insufficient to convert xylose to succinic acid, because xylose uptake requires larger amounts of ATP than the uptake of glucose [ 29 ]. An engineered E. Deletion of the glucose PEP-dependent phosphotransferase system of E. Moreover, a significant bottleneck of recombinant protein production in yeast occurs because of ATP-consuming protein biosynthesis [ 34 ].

Cell-free systems were developed to increase the efficiency of protein production, because reaction conditions are easier to modify compared with modifying the protein synthesis machinery of whole cells [ 35 ]. Thus, cell-free protein synthesis systems are used frequently to produce proteins such as toxic and membrane proteins that are difficult to synthesize using other systems [ 36 ] and are expected to produce antibodies.

Extracts of E. However, using these expensive phosphate donors increases the total cost of protein production. Thus, more efficient and economical methods for supplying ATP were developed to facilitate the use cell-free protein synthesis systems for industrial purposes.

For example, a less costly method for supplying ATP was developed using the glycolytic kinases present in cell extracts in the presence of added glucose [ 39 ]. Further, combinatorial use of glycolytic kinases and creatine kinase increases the ATP supply and improves protein production [ 39 ]. Recently, the hexametaphosphate was utilized as a phosphate donor to generate ATP in a cell-free protein synthesis system [ 40 ]. Conversely, permeable resting cells, which are treated with detergents or organic chemicals, were developed for bio-based fine chemical production [ 41 ].

These permeable cells synthesize target products and secrete them through the permeabilized cytoplasmic membrane using less ATP compared with impermeable whole cells, which require more ATP to efflux the product Fig. In aerobic fermentation using intact whole cells, the respiratory electron transport chain supplies ATP through the proton-motive force generated between the outer and inner surfaces of the cytoplasmic membrane and the mitochondrial inner membrane in prokaryotes and eukaryotes, respectively.

In contrast, permeable cells lose the ability to grow aerobically, because treatment with detergents or organic chemicals disrupts membranes, leading to the loss of ATP generation by the respiratory chain, although glycolysis continues to generate ATP [ 42 — 44 ]. Therefore, the ATP supply in permeable cells is usually lower compared with that of whole cells, but is remedied by coupling cellular glycolytic ATP generation with certain ATP-generating kinase reactions [ 45 ].

Further, systematic identification of genes that can be deleted to increase glycolytic ATP generation is required to enhance the ATP supply of permeable E.

ATP regeneration by heat-treated E. Conversely, another strategy to improve the glycolytic ATP supply involves inhibiting the ATP consuming glucose—glycogen bypass pathway of permeablized S.

Metabolic analysis indicates that antibody production is strongly related to the intracellular ATP supply in Chinese hamster ovary CHO cells, which are commonly used for industrial production of recombinant proteins [ 49 ]. The intracellular production of antibodies in stationary phase is higher than during the growth of CHO cell factories.

These results indicate that a higher ATP supply in stationary phase contributes to the higher level of intracellular biosynthesis of antibodies compared with the growth phase. In contrast, the introduction and enhancement of ATP-consuming reactions and pathways in cell factories is a strong force that drives metabolic flux in the desired direction [ 50 ].

For example, the butanol tolerance of Clostridium acetobutylicum is increased by overexpression of two ATP-consuming 6-phosphofructokinase and ATP-generating pyruvate kinase that increases the intracellular ATP supply [ 51 ] Fig. This strategy may improve butanol production in this engineered strain.

Further, metabolic analysis of Cyanobacteria sp. These studies indicate that the control of kinase reactions effectively improves ATP-consuming bioproduction by enhancing the intracellular ATP supply of cell factories.

The oxygen supply is critical for enhancing the ATP supply derived from reactions of the respiratory chain Fig. Recently, Tourmente et al. They found that mice that consume higher levels of oxygen produce sperm, which depend on ATP generation by the respiratory chain rather than glycolysis, swim faster compared with those from a mouse that consumes lower levels of oxygen [ 53 ].

Moreover, an accelerated oxygen supply increases the intracellular ATP levels during lactic acid production by an engineered strain of S. The increase in oxygen supply enhances cell growth and homo-fermentative lactic acid production by this engineered strain but not by the wild-type. The ATP requirement for enhanced cell growth and lactic acid production indicates that the respiratory ATP supply is the rate-limiting factor for growth and lactic acid production of this engineered strain [ 54 ].

Hayakawa et al. The results revealed that higher levels of SAM are produced because of an enhanced ATP supply generated by the respiratory chain, which is stimulated by the increase in TCA cycle flux [ 55 ]. Enhanced SAM production in Pichia pastoris is achieved by increasing the respiratory ATP supply regulated using pulsed-glycerol-feeding strategies [ 56 ].

In contrast, oxygen supply enhances intracellular ATP generation by the respiratory chain to supply ATP for ATP-consuming cellulose biosynthesis in Thermobifida fusca , although it inhibits cell growth [ 57 ].

Enhanced generation of ATP through the respiratory chain increases tolerance to toxic compounds. For example, alcohol toxicity is a significant problem for alcohol bioproduction. Higher ethanol concentrations produced anaerobically from pyruvic acid Fig. This decreases glycolytic generation of ATP and enhances ATP consumption while ethanol accumulation effectively reduces tolerance to ethanol [ 58 ]. In contrast, a butanol tolerant mutant of S.

In the final progeny, 21 of the 34 up-regulated proteins are predicted components of mitochondria, including 12 proteins of the respiratory chain [ 58 ].

These results indicate that the respiratory ATP generated by mitochondria is critical to confer butanol tolerance upon S. Conversely, mutant E. Similarly, deletion of genes encoding components of respiratory chain ATP synthase enhances the glycolytic ATP generation in permeable E.

This enhanced glycolytic ATP generation is attributed to an increase in the expression levels of glycolytic enzymes in response to the decreased respiratory generation of ATP. Recently, Wu et al. To further improve the ATP supply of cell factories, a combination of some of strategies shown in this review may be effective. Generating multiple deletions of ATP-consuming proteins is considered a new strategy, because technology to delete multiple genes is available [ 61 — 63 ].

Further, deletion or overexpression of global regulators may enhance total energy metabolism. Novel strategies to increase ATP mass are critical to implement further improvements in bioproduction, such as engineering de novo ATP biosynthesis via the pentose phosphate pathway, which is accompanied by an increase in the total amounts of all adenine nucleotides.

Further, an increase in other nucleotide triphosphates is critical for other specific reactions. Engineering the nucleotide synthesis pathway will be essential to control the balance of these nucleotide triphosphates. In contrast, enhancing cell tolerance to products is strongly dependent on the intracellular ATP supply, and its enhancements represent an effective strategy to increase cellular tolerance [ 19 , 51 , 58 ].

Your metabolism is the collection of chemical reactions that occur in your cells to sustain life. Some of these reactions use stored energy to build things up, which we call anabolism , while other reactions break things down, releasing energy that can be stored for future use, and this is called catabolism.

It took a lot of energy to organize those blocks into that complex structure, and breaking the blocks apart releases that energy and frees the blocks so that they can be built back up into new things.

Your body does exactly that when you eat your food. Here's a brief video lecture that summarizes this concept. Living things break down the three major categories of foods proteins, fats, and carbohydrates into their constituent parts, the individual lego blocks, for two reasons.

ATP Adenosine tri-phosphate is an important molecule found in all living things. The energy holding that phosphate molecule is now released and available to do work for the cell. When the cell has extra energy gained from breaking down food that has been consumed or, in the case of plants, made via photosynthesis , it stores that energy by reattaching a free phosphate molecule to ADP, turning it back into ATP.

Read More. The same chemical reaction that lights up fireflies on a warm summer night can also reveal microorganisms in water. Fireflies glow when adenosine triphosphate ATP molecules react with the From editor: Casey Oliver, guest blogger and one of our valued customers, proves that microbes can lurk anywhere — including the gym.

Update your browser to view this website correctly. Update my browser now. What is ATP and what does it do? What is the benefit to me? Want to learn more? And Why Should You Care? Related Posts How to Mitigate Biofouling in Your Industrial Process Using 2 nd Generation ATP Microorganisms can wreak havoc in industrial processes in a number of ways — from slime formation that causes paper breaks and excessive downtime in papermaking facilities, to costly