Thermophilic Enzymes’ Stability?

This review discusses the importance of thermostability in the application of enzymes in the industry, focusing on the most important enzymes produced by thermophilic bacteria, such as starch-degrading enzymes, celluloses, hemicelluloses, proteases, and more. Enzymes and exopolysaccharides (EPSs) are of special biotechnological interest due to their unusual properties. Enzyme encapsulation can provide a microenvironment that increases thermal stability and facilitates enzymatic activity at high temperatures.

Thermophilic bacteria effectively manage instability of the plasma membrane, inactivation of enzymes, instability of DNA, and other hostile physiological variations at elevated temperatures. Thermophilic enzymes are generally more thermally stable but less active at moderate temperatures than their mesophilic counterparts. They are more stable at all temperatures due to increased maximal stability and decreased heat capacity of unfolding.

Thermophilic proteins maintain their stability at high temperatures (80-100°C), with a direct relationship between environmental growth temperature and their stability. Some intracellular enzymes get their high thermostability from intracellular factors, which serve to stabilize proteins in a thermophilic environment by decreasing overall protein flexibility.

Thermophilic enzymes are generally more thermally stable but less active at moderate temperatures than their mesophilic counterparts. They withstand high temperatures by altering their structure, keeping the overall stability. Increased hydrogen bonding and more ionic bonds between amino acids in the protein structure contribute to the stability of the enzyme.

The objectives of this paper are to describe the unique properties of enzymes isolated from thermophilic microorganisms and discuss some of the potential applications of these enzymes in the industry.

Why are some enzymes more stable to thermal treatment than others?

Abstract. In general, enzyme thermostability is an intrinsic property, determined by the primary structure of the protein. However, external environmental factors including cations, substrates, co-enzymes, modulators, polyols and proteins often increase enzyme thermostability. With some exceptions, enzymes present in thermophiles are more stable than their mesophilic counterparts. Some organisms produce enzymes with different thermal stability properties when grown at lower and higher temperatures. There are commercial advantages in carrying out enzymic reactions at higher temperatures. Some industrial enzymes exhibit high thermostability. More stable forms of other industrial enzymes are eagerly being sought.

Vieille C, Burdette DS, Zeikus JG. Vieille C, et al. Biotechnol Annu Rev. 1996;2:1-83. doi: 10. 1016/s1387-265670006-1. Biotechnol Annu Rev. 1996. PMID: 9704095 Review.

Thermophilic enzymes and their biotechnological potential.

How do thermophiles stabilize existing proteins in elevated temperatures?

Proteins from archaea tend to be more compact due to tighter packing126 while thermophile bacteria tend to be stabilized by salt bridges. Salt bridges between pairs of charged residues produce bigger enhancements in protein stability at elevated temperatures due to a reduction in the dielectric constant of water.

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Why do enzymes work better at warmer temperatures?

Temperature. Higher temperature generally causes more collisions among the molecules and therefore increases the rate of a reaction. More collisions increase the likelihood that substrate will collide with the active site of the enzyme, thus increasing the rate of an enzyme-catalyzed reaction. Above a certain temperature, activity begins to decline because the enzyme begins to denature. The rate of chemical reactions therefore increases with temperature but then decreases as enzymes denature.

PH. Each enzyme has an optimal pH. A change in pH can alter the ionization of the R groups of the amino acids. When the charges on the amino acids change, hydrogen bonding within the protein molecule change and the molecule changes shape. The new shape may not be effective.

The diagram below shows that pepsin functions best in an acid environment. This makes sense because pepsin is an enzyme that is normally found in the stomach where the pH is low due to the presence of hydrochloric acid. Trypsin is found in the duodenum, and therefore, its optimum pH is in the neutral range to match the pH of the duodenum.

Why is thermal stability?

Thermal stability is a crucial concept in chemistry, materials science, and engineering, referring to a substance’s ability to resist chemical or physical changes when exposed to elevated temperatures. It is essential for designing products and processes that can withstand high-temperature environments. Thermally stable compounds can endure high temperatures, allowing for controlled and efficient chemical processes. In materials science and engineering, thermal stability is crucial for designing materials that can withstand extreme conditions, such as aerospace components and electronic devices operating in hot environments. High thermal stability is also essential for energy storage systems like batteries and supercapacitors, as well as in power plants and renewable energy technologies. In the pharmaceutical and food industry, thermal stability testing is essential to assess product shelf life and safety. Understanding the thermal stability of materials is also crucial in assessing their environmental impact, as some materials release harmful emissions when exposed to high temperatures, contributing to pollution and environmental degradation.

What makes a protein thermally stable?

Protein engineering techniques, such as site-directed and random mutagenesis, directed evolution, and comparative methods, have been used to enhance the thermostability of target proteins. Mesophilic proteins’ stability can be improved by comparing them to thermophilic homologs. Molecular dynamics analysis can be used to understand the unfolding process and design stabilizing mutations. Rational protein engineering includes mutations that truncate loops, increase salt bridges or hydrogen bonds, and introduce disulfide bonds. Ligand binding can also increase protein stability, particularly when purified.

Various forces, such as hydrophobic interactions, electrostatic interactions, and the presence of disulfide bonds, contribute to the thermostability of a protein. The overall hydrophobicity in a protein is responsible for its thermostability. Electrostatic interactions, such as salt bridges and hydrogen bonds, are necessary for protein and enzyme stability. Disulfide bonds, which present covalent cross-linkages between polypeptide chains, are the strongest force. Glycosylation can also improve protein thermostability by stereoelectronic effects in stabilizing interactions between carbohydrate and protein. Cyclizing enzymes, such as Intein cyclization and SpyTag/SpyCatcher cyclization, have been applied to increase the thermostability of many enzymes.

Poisonous fungi, such as Thermus thermophilus, Thermus aquaticus, and Pyrococcus furiosus, contain thermostable toxins, which cannot be removed by heat and pose a concern for food safety.

How do thermophilic enzymes survive?

Thermophiles can survive a wide range of temperatures, indicating they can elicit a prompt physiological response to environmental changes and form a functional network within cells by maintaining the optimal expression status of certain genes. The transcriptome and proteome data at the opposite sides of central dogma represent the gene expression status in thermophiles, and the integration of these two sets of gene expression data forms a solid foundation to pursue the adaptive mechanisms of thermophiles at high temperatures.

The assembly of genes into operons is an important adaptation process of microbes to environmental changes, with approximately half of the genes in those species located in operon structures. Euryarchaeotal methanogens have the highest density of operons, on average 60, while thermophiles have ∼43–56. The operon structure is believed to be more stable in thermophiles than non-thermophiles. The expression statuses of operon genes are correlated with thermophily, with approximately 250 genes expressed temperature-dependently in Thermoanaerobacter tengcongensis and most differential genes at the mRNA level strongly correlated with the protein level.

Operon regulation is an important mode to retain thermophile survival, as genes located within an operon could be economically co-regulated responding to a stimulus. Global regulators, such as CRP, IHF, FNR, FIS, ArcA, Lrp, and H-NS, have been reported in E. coli, which corresponds to the transcriptional regulation of 50 of E. coli genes. These global regulatory systems sometimes overlap and can cross-talk, such as σ 32, a heat-shock transcription factor, regulating not only the expression of heat-shock response proteins but also the chaperon proteins.

In some cases, the response of genes to different stresses are common, not only to heat but also to other conditions. Therefore, it is possible to deduce that there are global regulator systems in thermophiles that may respond not only to temperature but also to other stresses by regulating the expression of gene clusters.

What stabilizes an enzyme?

Finally, enzymes may be stabilized by encapsulation within a matrix such as a cross-linked network, a film or bulk polymer, (3, 26−32) This gives very good control over the physical environment surrounding the enzyme, and can yield high stabilities, but can also reduce the ability of substrate to diffuse to the enzyme …

How does temperature affect the stability of enzymes?

As temperature increases so do the rate of enzyme reactions. A ten degree centigrade rise in temperature will increase the activity of most enzymes by 50% to 100%. Variations in reaction temperature as small as 1 or 2 degrees may introduce changes of 10% to 20% in the results. This increase is only up to a certain point until the elevated temperature breaks the structure of the enzyme. Once the enzyme is denatured, it cannot be repaired. As each enzyme is different in its structure and bonds between amino acids and peptides, the temperature for denaturing is specific for each enzyme. Because most animal enzymes rapidly become denatured at temperatures above 40°C, most enzyme determinations are carried out somewhat below that temperature.

Over a period of time, enzymes will be deactivated at even moderate temperatures. Storage of enzymes at 5°C or below is generally the most suitable. Lower temperatures lead to slower chemical reactions. Enzymes will eventually become inactive at freezing temperatures but will restore most of their enzyme activity when temperatures increase again, while some enzymes lose their activity when frozen.

The temperature of a system is to some extent a measure of the kinetic energy of the molecules in the system. Collisions between all molecules increase as temperature increases. This is due to the increase in velocity and kinetic energy that follows temperature increases. With faster velocities, there will be less time between collisions. This results in more molecules reaching the activation energy, which increases the rate of the reactions. Since the molecules are also moving faster, collisions between enzymes and substrates also increase. Thus the lower the kinetic energy, the lower the temperature of the system and, likewise, the higher the kinetic energy, the greater the temperature of the system.

Why are thermophilic proteins more stable?

It has been suggested that increased polar surface area contributes to the greater stability of the thermophilic proteins (Haney et al., 1997; Vogt and Argos, 1997; Vogt et al., 1997). Here, we have divided protein surfaces into buried and exposed parts and evaluated the contribution of polar and non-polar atoms.

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What makes a protein more stable?

Cerevisiae, protein stability depends on the nature of the N-terminal amino acid. Amino acids such as glycine, methionine, threonine, alanine, and cysteine stabilize the protein when they are present at its N-terminal end.

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Why can thermophiles survive in high temperature?

Environmental changes such as temperature shifts induce genomic evolution, which in turn provides the bacteria with thermal-tolerant abil- ities to survive under high temperatures. Such evolutionary changes could be achieved through horizontal gene transfer (HGT), gene loss, or gene mutations.