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42-446: CLH may refer to: Science [ edit ] Chlorophyllase , an enzyme Hydrogen chloride , a chemical compound Companies [ edit ] CLH (company) , a Spanish petroleum logistics company comprising Compañía Logística de Hidrocarburos and others CLH Pipeline System (CLH-PS), a UK system run by Compañía Logística de Hidrocarburos Lufthansa CityLine (ICAO code),

84-529: A is comparable to that of acetic acid . Solutions of salts such as BeCl 2 or Al(NO 3 ) 3 in water are noticeably acidic ; the hydrolysis can be suppressed by adding an acid such as nitric acid , making the solution more acidic. Hydrolysis may proceed beyond the first step, often with the formation of polynuclear species via the process of olation . Some "exotic" species such as Sn 3 (OH) 2+ 4 are well characterized. Hydrolysis tends to proceed as pH rises leading, in many cases, to

126-549: A German airline Coolah Airport , IATA airport code "CLH" See also [ edit ] CLHS (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title CLH . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=CLH&oldid=1078713118 " Category : Disambiguation pages Hidden categories: Short description

168-488: A more technical discussion of what occurs during such a hydrolysis, see Brønsted–Lowry acid–base theory . Acid–base-catalysed hydrolyses are very common; one example is the hydrolysis of amides or esters . Their hydrolysis occurs when the nucleophile (a nucleus-seeking agent, e.g., water or hydroxyl ion) attacks the carbon of the carbonyl group of the ester or amide . In an aqueous base, hydroxyl ions are better nucleophiles than polar molecules such as water. In acids,

210-452: A significant rate in vivo. For example, it is estimated that in each human cell 2,000 to 10,000 DNA purine bases turn over every day due to hydrolytic depurination, and that this is largely counteracted by specific rapid DNA repair processes. Hydrolytic DNA damages that fail to be accurately repaired may contribute to carcinogenesis and ageing . Metal ions are Lewis acids , and in aqueous solution they form metal aquo complexes of

252-423: Is saponification : cleaving esters into carboxylate salts and alcohols . In ester hydrolysis , the hydroxide ion nucleophile attacks the carbonyl carbon. This mechanism is supported by isotope labeling experiments. For example, when ethyl propionate with an oxygen-18 labeled ethoxy group is treated with sodium hydroxide (NaOH), the oxygen-18 is completely absent from the sodium propionate product and

294-457: Is sucrose (table sugar). Hydrolysis of sucrose yields glucose and fructose . Invertase is a sucrase used industrially for the hydrolysis of sucrose to so-called invert sugar . Lactase is essential for digestive hydrolysis of lactose in milk; many adult humans do not produce lactase and cannot digest the lactose in milk. The hydrolysis of polysaccharides to soluble sugars can be recognized as saccharification . Malt made from barley

336-420: Is also known to function in the esterification of Chlide and transesterification . The enzyme functions optimally at pH 8.5 and 50 °C. Of high importance to all photosynthetic organisms is chlorophyll, and so, its synthesis and breakdown are closely regulated throughout the entire life cycle of the plant. Chlorophyll breakdown is most evident in seasonal changes as the plants lose their green color in

378-450: Is also thought to be involved in turnover and homeostasis of chlorophylls. Chlorophyllase catalysis of the initial step of chlorophyll breakdown is important for plant development and survival. The breakdown serves as a prerequisite in the detoxification of the potentially phototoxic chlorophyll and chlorophyll intermediates as it accompanies leaf senescence to non-fluorescent catabolites. Rapid degradation of chlorophyll and its intermediates

420-690: Is chlorophyllide. Chlorophyllide is then broken down to Pheophorbide a . After Pheophorbide a is formed, the porphyrin ring is cleaved by Pheophorbide a oxygenase (PAO) to form RCC ( red chlorophyll catabolite ) causing the plant to lose its green color. RCC is then broken down into pFCC. Citrus sinesis and Chenopodium album were the first plants from which the genes encoding chlorophyllase were isolated. These experiments revealed an uncharacteristic encoded sequence (21 amino acids in Citrus sinensis and 30 amino acids in Chenopodium album ) located on

462-415: Is different from Wikidata All article disambiguation pages All disambiguation pages Chlorophyllase Chlorophyllase can be found in the chloroplast , thylakoid membrane and etioplast of at least higher plants such as ferns, mosses, brown and red algae and diatoms. Chlase is the catalyst for the hydrolysis of chlorophyll to produce chlorophyllide (also called Chlide) and phytol . It

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504-519: Is formed, and the fatty acids react with the base, converting them to salts. These salts are called soaps, commonly used in households. In addition, in living systems, most biochemical reactions (including ATP hydrolysis) take place during the catalysis of enzymes . The catalytic action of enzymes allows the hydrolysis of proteins , fats, oils, and carbohydrates . As an example, one may consider proteases (enzymes that aid digestion by causing hydrolysis of peptide bonds in proteins ). They catalyze

546-403: Is needed to place the amide group in the proper position for catalysis. The necessary contacts between an enzyme and its substrates (proteins) are created because the enzyme folds in such a way as to form a crevice into which the substrate fits; the crevice also contains the catalytic groups. Therefore, proteins that do not fit into the crevice will not undergo hydrolysis. This specificity preserves

588-460: Is not consistent with degreening during natural senescence. Finally, there is evidence that chlorophyllase has been found in the inner envelope membrane of chloroplast where it does not come in contact with chlorophyll. Recent studies inspired by inconsistent data revealed that chlorophyllase in Citrus lacking the 21 amino sequence on the N-terminal results in extensive chlorophyll breakdown and

630-648: Is related to energy metabolism and storage. All living cells require a continual supply of energy for two main purposes: the biosynthesis of micro and macromolecules, and the active transport of ions and molecules across cell membranes. The energy derived from the oxidation of nutrients is not used directly but, by means of a complex and long sequence of reactions, it is channeled into a special energy-storage molecule, adenosine triphosphate (ATP). The ATP molecule contains pyrophosphate linkages (bonds formed when two phosphate units are combined) that release energy when needed. ATP can undergo hydrolysis in two ways: Firstly,

672-464: Is stable 20 °C higher than other chlorophyllases. These other chlorophyllases can stay active at temperatures up to 55 °C. Ethylene induces the synthesis of chlorophyllase and promotes the degreening of citrus fruits. Chlorophyllase was detected in protein extracts of ethylene treated fruit. Ethylene treated fruits had chlorophyllase activity increased by 5 fold in 24 hours. Ethylene, more specifically, induces increased rates of transcription of

714-409: Is that the suborganelle compartments breaking down allowing a greater amount of enzyme activity. Chlorophyllide, the product of the reaction catalyzed by chlorophyllase, spontaneously combines with plant lipids such as phosphatidylcholine liposomes along with sulfoquinovosyl diacylglycerol . These two lipids cooperatively inhibit the activity of chlorophyllase, but this inhibition can be reversed by

756-404: Is the nucleophile . Biological hydrolysis is the cleavage of biomolecules where a water molecule is consumed to effect the separation of a larger molecule into component parts. When a carbohydrate is broken into its component sugar molecules by hydrolysis (e.g., sucrose being broken down into glucose and fructose ), this is recognized as saccharification . Hydrolysis reactions can be

798-402: Is therefore necessary to prevent cell damage due to the potential phototoxicity of chlorophyll. Chlorophyllase catalyzes the hydrolysis of ester bond to yield chlorophyllide and phytol. It reacts via transesterification or hydrolysis of a carboxylic ester in which its natural substrates are 13-OH-chlorophyll a, bacteriochlorophyll and chlorophyll a. Hydrolysis of chlorophyll starts with

840-532: Is used as a source of β-amylase to break down starch into the disaccharide maltose , which can be used by yeast to produce beer . Other amylase enzymes may convert starch to glucose or to oligosaccharides. Cellulose is first hydrolyzed to cellobiose by cellulase and then cellobiose is further hydrolyzed to glucose by beta-glucosidase . Ruminants such as cows are able to hydrolyze cellulose into cellobiose and then glucose because of symbiotic bacteria that produce cellulases. Hydrolysis of DNA occurs at

882-462: The N-terminal that was absent from the mature protein. The chlorophyllase enzyme is a smart choice as the rate limiting enzyme of the catabolic pathway since degreening and the expression of chlorophyllase is induced in ethylene-treated Citrus . Recent data, however, suggests that chlorophyllase is expressed at low levels during natural fruit development, when chlorophyll catabolism usually takes place. Also, some data suggests that chlorophyllase activity

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924-423: The attack of a carbonyl group of chlorophyll by the oxygen of the hydroxyl group of the crucial serine residue of the chlorophyllase. This attack forms a tetrahedral transition state. The double bond of the attacked carbonyl reforms and the serine is then esterified to chlorophyllide. The phytol group consequently leaves the compound and replaces the serine residue on the chlorophyllase enzyme. The addition of water to

966-463: The autumn; it is also evident in fruit ripening, leaf senescence and flowering. In this first step, chlorophyllase initiates the catabolism of chlorophyll to form chlorophyllide. Chlorophyll degradation occurs in the turnover of chlorophyll, as well as in the event of cell death caused by injuries, pathogenic attack, and other external factors. Chlorophyllase's role is two-fold as it functions in both de-greening processes, such as autumnal coloration, and

1008-415: The carbonyl group becomes protonated, and this leads to a much easier nucleophilic attack. The products for both hydrolyses are compounds with carboxylic acid groups. Perhaps the oldest commercially practiced example of ester hydrolysis is saponification (formation of soap). It is the hydrolysis of a triglyceride (fat) with an aqueous base such as sodium hydroxide (NaOH). During the process, glycerol

1050-518: The chlorophyllase gene. There is also evidence of a highly conserved serine lipase domain in the chlorophyllase enzyme that contains a serine residue that is essential for enzyme activity. Histidne and aspartic acid residues are also a part of the catalytic triad of chlorophyllase as a serine hydrolase . Specific inhibitors for the serine hydrolase mechanism, therefore, effectively inhibit the chlorophyllase enzyme. Also, mutations at these specific amino acid residues causes complete loss of function since

1092-429: The conversion of cellulose or starch to glucose . Carboxylic acids can be produced from acid hydrolysis of esters. Acids catalyze hydrolysis of nitriles to amides. Acid hydrolysis does not usually refer to the acid catalyzed addition of the elements of water to double or triple bonds by electrophilic addition as may originate from a hydration reaction . Acid hydrolysis is used to prepare monosaccharide with

1134-473: The degreening effect that should occur in vivo . This cleavage occurs in the chloroplast membrane fraction. Both the full chlorophyllase and the cleaved, mature chlorophyllase, however, experienced similar levels of activity in an in vitro assay. This data suggests that the mature protein comes in contact with its substrate more readily because of the N-terminal sequence and some natural regulation occurs that directly affects enzyme activity. Another possibility

1176-457: The direction of synthesis when the phosphate bonds have undergone hydrolysis. Monosaccharides can be linked together by glycosidic bonds , which can be cleaved by hydrolysis. Two, three, several or many monosaccharides thus linked form disaccharides , trisaccharides , oligosaccharides , or polysaccharides , respectively. Enzymes that hydrolyze glycosidic bonds are called " glycoside hydrolases " or "glycosidases". The best-known disaccharide

1218-468: The general formula M(H 2 O) n . The aqua ions undergo hydrolysis, to a greater or lesser extent. The first hydrolysis step is given generically as Thus the aqua cations behave as acids in terms of Brønsted–Lowry acid–base theory . This effect is easily explained by considering the inductive effect of the positively charged metal ion, which weakens the O−H bond of an attached water molecule, making

1260-401: The help of mineral acids but formic acid and trifluoroacetic acid have been used. Acid hydrolysis can be utilized in the pretreatment of cellulosic material, so as to cut the interchain linkages in hemicellulose and cellulose. Alkaline hydrolysis usually refers to types of nucleophilic substitution reactions in which the attacking nucleophile is a hydroxide ion . The best known type

1302-442: The hydrogen ion. The hydrolysis of peptides gives amino acids . Many polyamide polymers such as nylon 6,6 hydrolyze in the presence of strong acids. The process leads to depolymerization . For this reason nylon products fail by fracturing when exposed to small amounts of acidic water. Polyesters are also susceptible to similar polymer degradation reactions. The problem is known as environmental stress cracking . Hydrolysis

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1344-420: The hydrolysis of interior peptide bonds in peptide chains, as opposed to exopeptidases (another class of enzymes, that catalyze the hydrolysis of terminal peptide bonds, liberating one free amino acid at a time). However, proteases do not catalyze the hydrolysis of all kinds of proteins. Their action is stereo-selective: Only proteins with a certain tertiary structure are targeted as some kind of orienting force

1386-412: The hydroxide ions whereas the acetate ions combine with hydronium ions to produce acetic acid . In this case the net result is a relative excess of hydroxide ions, yielding a basic solution . Strong acids also undergo hydrolysis. For example, dissolving sulfuric acid ( H 2 SO 4 ) in water is accompanied by hydrolysis to give hydronium and bisulfate , the sulfuric acid's conjugate base . For

1428-407: The integrity of other proteins such as hormones , and therefore the biological system continues to function normally. Upon hydrolysis, an amide converts into a carboxylic acid and an amine or ammonia (which in the presence of acid are immediately converted to ammonium salts). One of the two oxygen groups on the carboxylic acid are derived from a water molecule and the amine (or ammonia) gains

1470-550: The liberation of a proton relatively easy. The dissociation constant , pK a , for this reaction is more or less linearly related to the charge-to-size ratio of the metal ion. Ions with low charges, such as Na are very weak acids with almost imperceptible hydrolysis. Large divalent ions such as Ca , Zn , Sn and Pb have a pK a of 6 or more and would not normally be classed as acids, but small divalent ions such as Be undergo extensive hydrolysis. Trivalent ions like Al and Fe are weak acids whose pK

1512-433: The mutations change the catalytic site of the chlorophyllase enzyme. Hydrolysis Hydrolysis ( / h aɪ ˈ d r ɒ l ɪ s ɪ s / ; from Ancient Greek hydro-  'water' and lysis  'to unbind') is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution , elimination , and solvation reactions in which water

1554-573: The precipitation of a hydroxide such as Al(OH) 3 or AlO(OH) . These substances, major constituents of bauxite , are known as laterites and are formed by leaching from rocks of most of the ions other than aluminium and iron and subsequent hydrolysis of the remaining aluminium and iron. Acetals , imines , and enamines can be converted back into ketones by treatment with excess water under acid-catalyzed conditions: RO·OR−H 3 O−O ; NR·H 3 O−O ; RNR−H 3 O−O . Acid catalysis can be applied to hydrolyses. For example, in

1596-441: The presence of Mg++, a divalent cation. The activity of chlorophyllase also depends on the pH and ionic content of the medium. The values of kcat and kcat/Km of chlorophyllase in the presence of chlorophyll showed pKa values of 6.3 and 6.7, respectively. Temperature also affects chlorophyllase activity. Wheat chlorophyllase is active from 25 to 75 °C. The enzyme is inactivated at temperatures above 85 °C. Wheat chlorophyllase

1638-412: The reaction cleaves the phytol off the enzyme. Next, through the reverse reaction, the oxygen on the hydroxy group from the water in the previous step attacks the carbonyl of the intermediate in order to form another tetrahedral transition state. The double bond of the carbonyl forms again and the serine residue returns to chlorophyllase and the ester of the chlorophyll is now a carboxylic acid. This product

1680-403: The removal of terminal phosphate to form adenosine diphosphate (ADP) and inorganic phosphate, with the reaction: Secondly, the removal of a terminal diphosphate to yield adenosine monophosphate (AMP) and pyrophosphate . The latter usually undergoes further cleavage into its two constituent phosphates. This results in biosynthesis reactions, which usually occur in chains, that can be driven in

1722-433: The reverse of a condensation reaction in which two molecules join into a larger one and eject a water molecule. Thus hydrolysis adds water to break down, whereas condensation builds up by removing water. Usually hydrolysis is a chemical process in which a molecule of water is added to a substance. Sometimes this addition causes both the substance and water molecule to split into two parts. In such reactions, one fragment of

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1764-489: The target molecule (or parent molecule) gains a hydrogen ion . It breaks a chemical bond in the compound. A common kind of hydrolysis occurs when a salt of a weak acid or weak base (or both) is dissolved in water. Water spontaneously ionizes into hydroxide anions and hydronium cations . The salt also dissociates into its constituent anions and cations. For example, sodium acetate dissociates in water into sodium and acetate ions. Sodium ions react very little with

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