Biological Sciences
Hydrolysis Reaction
Hydrolysis reaction is a chemical reaction that breaks down a compound into smaller molecules by adding water. In biological systems, hydrolysis is used to break down complex molecules such as carbohydrates, proteins, and lipids into their simpler components, which can then be used for energy or other cellular processes.
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4 Key excerpts on "Hydrolysis Reaction"
eBook - PDFWater in Biological and Chemical Processes
From Structure and Dynamics to Function
- Biman Bagchi(Author)
- 2013(Publication Date)
- Cambridge University Press(Publisher)
In the following we discuss these topics from a molecular perspective that has been beginning to emerge in recent years. 98 An essential chemical for life processes: water in biological functions 7.2 Role of water in enzyme kinetics Enzymes are well recognized as biological catalysts. According to the general kind of reaction they catalyze, enzymes are categorized into various classes, such as oxidoreductase, transferase, hydrolase, lyase, and isomerase, to name a few. Among them probably the best-known enzymes are hydrolases. They catalyze the breaking of bonds with the direct assistance/participation of water molecules. The reaction can be generally written in the following form A B þ H 2 O ! A OH þ B H In many cases, water turns into a proton and a hydroxyl anion and the A–B bond shown above breaks to make A + and B − . Therefore, a pair of electrons needs to be moved around, and electrostatics of the medium must play an important role. We discuss specific examples below. The digestion of carbohydrates and proteins not only requires these hydrolases but a sufficient amount of water is also necessary to execute the body’ s digestive mechanism. To show how these enzymes function in the body, we take the example of sucrase. Sucrase inhabits the surface of the microvilli on the intestinal mucosal membrane. It catalyzes the hydrolysis of sucrose, which is a disaccharide, into two monosaccharide units: glucose and fructose [2]. During the catalysis process, when sucrose binds to the active site of the enzyme (sucrase), the enzyme configuration is changed such that the oxygen bridge between the two monosaccharides is exposed to water molecules. Our second example is provided by proteases, which are another type of hydro- lases that catalyze the hydrolysis of peptide bonds in proteins. A general reaction scheme for proteases is shown in Reaction 7.1.
eBook - PDF- W. Brock Neely(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
172 158 Environmental Exposure from Chemicals I. INTRODUCTION Hydrolysis along with biodegradation (Chapter 6) and photodegradation (Chapters 8 and 9) is one of the significant environmental fate processes that act on many types of organic chemicals. The simple reaction shown in Equation I defines R -OH + x-+ H+ (1) the process. In this scheme a chemical transformation has occurred in which an organic molecule, R -X, reacts with water, forming a new carbon-oxygen bond and cleaving a carbon-X bond in the original molecule. The net effect is a direct displacement of X by OH. The importance of the scheme from an environmental point of view is that the resulting product is usually more easily degraded, metabolized and less toxic than the initial starting material. As knowledge of the fate and transport processes of chemicals increases, it is logical that the emphasis will change from field observation to prediction. Field experiments, where the chemical is added to an ecosystem and the disappearance is followed with time are very site specific. Information gained in this situation is very difficult to extrapolate to a new system. The predictive mode, on the other hand, requires a detailed knowledge both of the mechanism and the factors that perturb the mechanism. This entire book is devoted to the subject of prediction and the state of the art in understanding the various forces that are operating on a chemical. The present chapter will be confined to hydrolysis. Before attempting to assess the role of hydrolysis it is well to recognize that certain organic structures are resistant to attack. Table 1 illustrates the types of chemicals that are unreactive' while Table 2 lists functional groups that are potentially susceptible to hydrolysis. 1 • 2 Once a decision is made that the molecule can hydrolyze, it becomes important to have as much information as possible concerning the mechanism and laws governing the rate of reaction.
eBook - PDFIonic Liquids in the Biorefinery Concept
Challenges and Perspectives
- Rafal Bogel-Lukasik(Author)
- 2015(Publication Date)
- Royal Society of Chemistry(Publisher)
21 4.2.2.2.1 Enzymatic Hydrolysis of Biomass. Enzymatic hydrolysis is a process catalysed by a group of enzymes called cellulases, which feature a mixture of different enzymatic activities whose combined actions lead to the degradation of cellulose. The released saccharide compounds are the feed-stock for fermentation. 22 Enzymes are naturally occurring proteins that act as catalysts with high specificity. Enzymatic hydrolysis of lignocellulose has been studied as a method to depolymerize biomass into fermentable sugars for further conversion to biofuels and biochemical products. 23 The use of enzymes in the hydrolysis of cellulose is more advantageous than the use of chemical catalysts because enzymes are highly specific and can work under mild conditions; however, the enzymatic process is hindered by the high cost 101 Biomass Hydrolysis in Ionic Liquids of the commercially available enzymes meant for this purpose. When hydro-lysis is performed at high-solid loadings (≥15% of solids, w/w), enzymatic hydrolysis potentially offers lower processing costs because sugar and etha-nol concentrations are increased. 24 Commercialization of the enzymatic pro-cess is hindered because the costs of the currently available enzyme isolation and purification are very high. 25 4.2.2.2.2 Acid Hydrolysis of Biomass. Acid hydrolysis is a chemical pro-cess which, by using acid catalysts, transforms the polysaccharide chains, which form biomass (hemicellulose and cellulose), into their basic mono-mers. Such hydrolysis can be performed by using various kinds of acids such as sulfurous, hydrochloric, sulfuric, phosphoric, nitric and formic acids. Industrial processes for acid hydrolysis can be grouped into two types: those that employ concentrated acids and those that use dilute acids. With hydro-lysis processes that involve the use of strong acids, and which operate at low temperatures, high yields can be obtained (above 90% of the potential glu-cose).
eBook - PDF- Deniz Ekinci(Author)
- 2012(Publication Date)
- IntechOpen(Publisher)
Numerous hydrolases are now known, and they have been classified into many sequentially and structurally unrelated clans and families. Hydrolases are found in all living organisms, performing functions from simple digestion to regulation of the immune response, blood coagulation and glucose homeostasis (Bachovchin, 2001). Most of hydrolases are used in processing reactions, degrading proteins, carbohydrates and lipids in * Corresponding Author Medicinal Chemistry and Drug Design 236 many scientific and industrial disciplines. “How these enzymes work?” is a question that has attracted big attention over past decades (Henrissat, 1991, 1995). 1.4 Enzyme kinetics The section of biochemistry, which deals with enzymes, is termed “Enzymology”, whose a branch is known as “Enzyme kinetics” relevant to the study of enzyme mechanisms, their reaction rates and the conditions which affect these rates. Enzyme kinetics is a particular case of chemical kinetics as enzymes are acting as catalysts, i.e. they increase the rate of a reaction without modifying its overall standard Gibbs-energy change (NC-IUB, 1983). The rate of an enzymatic reaction is expressed as the change in concentration of one of its substrates or products versus time, and it may be the function of several parameters including enzyme and substrate concentrations, time, pH-value and temperature of the reaction medium, as well as of others, affecting the reaction rate. The study of various kinds of models of enzymatic reactions attain of great interest in research, as well as in industrial applications of these biocatalysts, enhancing our knowledge about these processes and/or estimating the values of useful variables and parameters of these systems (Hogan & Woodley, 2000). The rate equation of an enzymatic reaction is a mathematical expression illustrating the catalysis in terms of rate constants and reactant concentrations, and it should best fit the experimental data.
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