Phospholipase A1 is a phospholipase enzyme which removes the 1-acyl. Phospholipase A1 is an enzyme that resides in a class of enzymes called phospholipase that hydrolyze phospholipids into fatty acids, there are 4 classes, which are separated by the type of reaction they catalyze. In particular, phospholipase A1 specifically catalyzes the cleavage at the SN-1 position of phospholipids, forming a fatty acid and these enzymes are responsible for fast turnover rates of cellular phospholipids. In addition, lysophospholipids can be found as surfactants in food techniques and cosmetics, since PLA1 is found in many species, it has been found that there are different classes of this one specific enzyme based on the organism being studied. There are many variations of PLA1, differing slightly between each organism it is present in. Most notably, it can be found in cells such as plasma of rat livers and bovine brains, and can be found in metazoan parasites, protozoan parasites. PLA1 hydrolyzes nonionic substrates preferentially over ionic substrates, optimum pH conditions for PLA1 activity on neutral phospholipids is around 7.5, whereas the optimal conditions for PLA1 activity on acidic phospholipids is around 4.
The structure of a PLA1 is a monomer that contains the sequence, Gly-X-Ser-X-Gly. The serine is considered the site in the enzyme. PLA1’s contain a catalytic triad of Ser-Asp-His, with a variety of cysteine residues needed for disulfide bond formation, the cysteine residues are responsible for key structural motifs such as the lid domain and the B9 domain, both of which are lipid binding surface loops. These two loops can vary between each PLA1, for example, a PLA1 enzyme with a long lid domain and a long B9 domain constitute an extracellular PLA1 exhibiting triacylglycerol hydrolase activity. In contrast, a PLA1 enzyme that is considered more selective will have a lid and B9 domain that span 7-12 and 12-13 amino acids. Unlike other phospholipases such as PLA2, there is much that is unknown about PLA1 due to the lack of any efficient way to purify, express, PLA1 is currently commercially unavailable because of this. Lysophospholipids can be found as surfactants in food techniques and cosmetics, current research is being applied to determine suitable growth environments for PLA1 production.
In one particular study, it was found that PLA1 can be produced by S. cerevisiae, in these PLA1 producing cultures, increasing the nitrogen and carbon sources can lead to increase in PLA1 yields. In the early 1900s, an observation was made, showing an accumulation of free fatty acids after incubation of pancreatic juice with phosphatidylcholine. In the 1960s, it was discovered to be that enzymes catalyze this fatty acid cleavage in multiple ways and this particular reaction is catalyzed by PLA1, while the reaction at the sn-2 position is catalyzed by phospholipase A2
Pectinesterase is a ubiquitous cell-wall-associated enzyme that presents several isoforms that facilitate plant cell wall modification and subsequent breakdown. It is found in all plants as well as in some bacteria. Pectinesterase functions primarily by altering the localised pH of the cell resulting in alterations in cell wall integrity. Pectinesterase catalyses the de-esterification of pectin into pectate and methanol, pectin is one of the main components of the plant cell wall. In plants, pectinesterase plays an important role in cell wall metabolism during fruit ripening, in plant bacterial pathogens such as Erwinia carotovora and in fungal pathogens such as Aspergillus niger, pectinesterase is involved in maceration and soft-rotting of plant tissue. Plant pectinesterases are regulated by pectinesterase inhibitors, which are ineffective against microbial enzymes, recent studies have shown that the manipulation of pectinesterase expression can influence numerous physiological processes. Pectinesterase has shown to play a role in a plants response to pathogen attack.
Pectinesterase action on the components of the plant cell wall can produce two diametrically opposite effects, the first being a contribution to the stiffening of the cell wall by producing blocks of unesterified carboxyl groups that can interact with calcium ions forming a pectate gel. The other being that proton release may stimulate the activity of cell wall hydrolases contributing to cell wall loosening, pectins form approximately 35% of the dry weight of dicot cell walls. They are polymerised in the cis Golgi, methylesterified in the medial Golgi, pectin biochemistry can be rather complicated but put simply, the pectin backbone comprises 3 types of polymer, rhamnogalacturonan I, rhamnogalacturonan II. Homogalacturonan is highly methyl-esterified when exported into cell walls and is subsequently de-esterified by the action of pectinesterase, most of the purified plant pectinesterases have neutral or alkaline isoelectric points and are bound to the cell wall via electrostatic interactions.
Pectinesterases can however display acidic isoelectric points as detected in soluble fractions of plant tissues, alternatively it was thought that fungal pectinesterases had a random activity resulting in the de-esterification of single GalA residues per enzyme/substrate interactions. It has now shown that some plant pectinesterase isoforms may exhibit both mechanisms and that such mechanisms are driven by alterations in pH. The optimal pH of higher plants is usually between pH7 and pH8 although the pH of pectinesterase from fungi and bacteria is usually lower than this. PE proteins are synthesised as pre-proteins of 540-580 amino acids possessing a signal sequence and this terminal extension is eventually removed to yield a mature protein of 34-37 kDa. Most PEs lack consensus sequences for N-glycosylation in the mature protein and temporal regulation of pectinestersae activity during plant development is based on a large family of isoforms. The signal peptide pre-region is required for targeting the enzyme to the endoplasmic reticulum and these N-terminal regions contain several glycosylation sites and it is thought that these sites play a role in targeting.
Pectinesterase is thought to be secreted to the apoplasm with highly methylated pectin although at some point along this pathway the N-terminal pro-peptide is cleaved off
Enzymes /ˈɛnzaɪmz/ are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions, the molecules at the beginning of the process upon which enzymes may act are called substrates and the enzyme converts these into different molecules, called products. Almost all metabolic processes in the cell need enzymes in order to occur at rates fast enough to sustain life, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. The study of enzymes is called enzymology, enzymes are known to catalyze more than 5,000 biochemical reaction types. Most enzymes are proteins, although a few are catalytic RNA molecules, enzymes specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the rate of a reaction by lowering its activation energy, some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5-phosphate decarboxylase, which allows a reaction that would take millions of years to occur in milliseconds.
Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules, inhibitors are molecules that decrease enzyme activity, many drugs and poisons are enzyme inhibitors. An enzymes activity decreases markedly outside its optimal temperature and pH, some enzymes are used commercially, for example, in the synthesis of antibiotics. French chemist Anselme Payen was the first to discover an enzyme, diastase and he wrote that alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells. In 1877, German physiologist Wilhelm Kühne first used the term enzyme, the word enzyme was used to refer to nonliving substances such as pepsin, and the word ferment was used to refer to chemical activity produced by living organisms. Eduard Buchner submitted his first paper on the study of yeast extracts in 1897, in a series of experiments at the University of Berlin, he found that sugar was fermented by yeast extracts even when there were no living yeast cells in the mixture.
He named the enzyme that brought about the fermentation of sucrose zymase, in 1907, he received the Nobel Prize in Chemistry for his discovery of cell-free fermentation. Following Buchners example, enzymes are usually named according to the reaction they carry out, the biochemical identity of enzymes was still unknown in the early 1900s. Sumner showed that the enzyme urease was a protein and crystallized it. These three scientists were awarded the 1946 Nobel Prize in Chemistry, the discovery that enzymes could be crystallized eventually allowed their structures to be solved by x-ray crystallography. This high-resolution structure of lysozyme marked the beginning of the field of structural biology, an enzymes name is often derived from its substrate or the chemical reaction it catalyzes, with the word ending in -ase
Monoacylglycerol lipase, known as MAG lipase, MAGL, MGL or MGLL is a protein that, in humans, is encoded by the MGLL gene. MAGL is a 33-kDa, membrane-associated member of the hydrolase superfamily. The catalytic triad has been identified as Ser122, His269, monoacylglycerol lipase functions together with hormone-sensitive lipase to hydrolyze intracellular triglyceride stores in adipocytes and other cells to fatty acids and glycerol. MGLL may complement lipoprotein lipase in completing hydrolysis of monoglycerides resulting from degradation of lipoprotein triglycerides, monoacylglycerol lipase is a key enzyme in the hydrolysis of the endocannabinoid 2-arachidonoylglycerol. It converts monoacylglycerols to the fatty acid and glycerol. The contribution of MAGL to total brain 2-AG hydrolysis activity has been estimated to be ~85%, chronic inactivation of MAGL results in massive elevations of brain 2-AG in mice, along with marked compensatory downregulation of CB1 receptors in selective brain areas.
The enzyme was reported to be inhibited by URB754, however this inhibitor has subsequently shown to be inactive. JZL184 is the first efficacious and selective inhibitor of MAGL that can elevate brain 2-AG levels in vivo, JZL184 has >300-fold selectivity for MAGL over other brain serine hydrolases, including FAAH
In biochemistry, a cholinesterase or choline esterase is an esterase that lyses choline-based esters, several of which serve as neurotransmitters. Thus, it is either of two enzymes that catalyze the hydrolysis of these cholinergic neurotransmitters, such as breaking acetylcholine into choline and these reactions are necessary to allow a cholinergic neuron to return to its resting state after activation. The main type for that purpose is acetylcholinesterase, it is mainly in chemical synapses. The other type is butyrylcholinesterase, it is mainly in the blood plasma. The two types of cholinesterase are acetylcholinesterase and butyrylcholinesterase, the difference between the two types has to do with their respective preferences for substrates, the former hydrolyses acetylcholine more quickly, the latter hydrolyses butyrylcholine more quickly. But such usage is now outdated, the current, unambiguous HGNC names, acetylcholinesterase exists in multiple molecular forms. In the mammalian brain the majority of AChE occurs as a tetrameric, the butyl and butyryl syllables both refer to butane with one of its terminal methyl groups substituted.
The half-life of BCHE is approximately 10 to 14 days, BCHE levels may be reduced in patients with advanced liver disease. The decrease must be greater than 75% before significant prolongation of neuromuscular blockade occurs with succinylcholine, in 1968, Walo Leuzinger et al. successfully purified and crystallized acetylcholinesterase from electric eels at Columbia University, NY. The 3D structure of acetylcholinesterase was first determined in 1991 by Joel Sussman et al. using protein from the Pacific electric ray, clinically useful quantities of butyrylcholinesterase were synthesized in 2007 by PharmAthene, through the use of genetically modified goats. An absence or mutation of the BCHE enzyme leads to a condition known as pseudocholinesterase deficiency. This is a silent condition that manifests itself only when people that have the deficiency receive the muscle relaxants succinylcholine or mivacurium during a surgery, pseudocholinesterase deficiency may affect local anaesthetic selection in dental procedures.
The selection of a solution is recommended in such patients. Elevation of plasma BCHE levels was observed in 90. 5% cases of myocardial infarction. The presence of ACHE in the fluid may be tested in early pregnancy. A sample of fluid is removed by amniocentesis, and presence of ACHE can confirm several common types of birth defect, including abdominal wall defects. BCHE can be used as an agent against nerve gas. A cholinesterase inhibitor suppresses the action of the enzyme, the enzyme acetylcholine esterase breaks down the neurotransmitter acetylcholine, which is released at nerve and muscle junctions, in order to allow the muscle or organ to relax
Biomolecular structure is the intricate folded, three-dimensional shape that is formed by a molecule of protein, DNA, or RNA, and that is important to its function. The structure of molecules may be considered at any of several length scales ranging from the level of individual atoms to the relationships among entire protein subunits. This useful distinction among scales is often expressed as a decomposition of molecular structure into four levels, secondary, the scaffold for this multiscale organization of the molecule arises at the secondary level, where the fundamental structural elements are the molecules various hydrogen bonds. The terms primary, secondary and quaternary structure were introduced by Kaj Ulrik Linderstrøm-Lang in his 1951 Lane Medical Lectures at Stanford University, the primary structure of a biopolymer is the exact specification of its atomic composition and the chemical bonds connecting those atoms. For a typical unbranched, un-crosslinked biopolymer, the structure is equivalent to specifying the sequence of its monomeric subunits.
Primary structure is sometimes mistakenly termed primary sequence, but there is no such term, the primary structure of a nucleic acid molecule refers to the exact sequence of nucleotides that comprise the whole molecule. Often, the primary structure encodes motifs that are of functional importance. The secondary structure is the pattern of hydrogen bonds in a biopolymer, secondary structure is formally defined by the hydrogen bonds of the biopolymer, as observed in an atomic-resolution structure. In proteins, the structure is defined by patterns of hydrogen bonds between backbone amide and carboxyl groups, where the DSSP definition of a hydrogen bond is used. In nucleic acids, the structure is defined by the hydrogen bonding between the nitrogenous bases. For proteins, the bonding is correlated with other structural features. Many other less formal definitions have been proposed, often applying concepts from the geometry of curves, such as curvature. Structural biologists solving a new structure will sometimes assign its secondary structure by eye.
The secondary structure of an acid molecule refers to the base pairing interactions within one molecule or set of interacting molecules. The secondary structure of biological RNAs can often be uniquely decomposed into stems, these elements or combinations of them can be further classified, e. g. tetraloops and stem-loops. There are many secondary structure elements of importance to biological RNAs. Famous examples include the Rho-independent terminator stem-loops and the transfer RNA cloverleaf, there is a minor industry of researchers attempting to determine the secondary structure of RNA molecules. Approaches include both experimental and computational methods, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates
A cutinase is an enzyme that catalyzes the chemical reaction cutin + H2O ⇌ cutin monomers Thus, the two substrates of this enzyme are cutin and H2O, whereas its product is cutin monomer. This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds, the systematic name of this enzyme class is cutin hydrolase. Aerial plant organs are protected by a cuticle composed of an insoluble polymeric structural compound, plant pathogenic fungi produce extracellular degradative enzymes that play an important role in pathogenesis. They include cutinase, which hydrolyses cutin, facilitating fungus penetration through the cuticle, inhibition of the enzyme can prevent fungal infection through intact cuticles. Cutinase is a serine esterase containing the classical Ser, the protein belongs to the alpha-beta class, with a central beta-sheet of 5 parallel strands covered by 5 helices on either side of the sheet. The active site cleft is partly covered by 2 thin bridges formed by amino acid side chains, the protein contains 2 disulfide bridges, which are essential for activity, their cleavage resulting in complete loss of enzymatic activity.
Two cutinase-like proteins have been found in the genome of the bacteria Mycobacterium tuberculosis, garcia-Lepe R, Nuero OM, Reyes F, Santamaria F. Lipases in autolysed cultures of filamentous fungi. Hydrolysis of plant cuticle by plant pathogens, amino acid composition, and molecular weight of two isozymes of cutinase and a nonspecific esterase from Fusarium solani f. pisi. Hydrolysis of plant cuticle by plant pathogens, properties of cutinase I, cutinase II, and a nonspecific esterase isolated from Fusarium solani pisi. Media related to Cutinase at Wikimedia Commons This article incorporates text from the public domain Pfam and InterPro IPR000675
In chemistry thioesters are compounds with the functional group R–S–CO–R. They are the product of esterification between an acid and a thiol. In biochemistry, the best-known thioesters are derivatives of coenzyme A, e. g. acetyl-CoA, for example, thioacetate esters are commonly prepared by alkylation of potassium thioacetate, CH3COSK + RX → CH3COSR + KCl The analogous alkylation of an acetate salt is rarely practiced. Acid anhydrides and some give thioesters upon treatment with thiols in the presence of a base. Thioesters can be prepared from alcohols by the Mitsunobu reaction. They arise via carbonylation of alkynes and alkenes in the presence of thiols, the carbonyl center in thioesters is reactive toward nucleophiles, even water. A reaction unique to thioesters is the Fukuyama coupling, in which the thioester is coupled with an organozinc halide by a palladium catalyst to give a ketone, the C-H groups adjacent to the carbonyl in thioesters are mildly acidic and undergo aldol condensations.
This kind of reaction occurs in the biosynthesis of fatty acids, thioesters are common intermediates in many biosynthetic reactions, including the formation and degradation of fatty acids and mevalonate, precursor to steroids. Examples include malonyl-CoA, acetoacetyl-CoA, propionyl-CoA, and cinnamoyl-CoA, acetogenesis proceeds via the formation of acetyl-CoA. The biosynthesis of lignin, which comprises a fraction of the Earths land biomass. These thioesters arise analogously to those prepared synthetically, the difference being that the agent is ATP. In addition, thioesters play an important role in the tagging of proteins with ubiquitin, oxidation of the sulfur atom in thioesters is postulated in the bioactivation of the antithrombotic prodrugs ticlopidine and prasugrel. As posited in a Thioester World, thioesters are possible precursors to life, as de Duve explains, It is revealing that thioesters are obligatory intermediates in several key processes in which ATP is either used or regenerated.
Thioesters are involved in the synthesis of all esters, including those found in complex lipids and they participate in the synthesis of a number of other cellular components, including peptides, fatty acids, terpenes and others. In addition, thioesters are formed as key intermediates in several particularly ancient processes that result in the assembly of ATP, in both these instances, the thioester is closer than ATP to the process that uses or yields energy. In other words, thioesters could have played the role of ATP in a thioester world initially devoid of ATP. Eventually, thioesters could have served to usher in ATP through its ability to support the formation of bonds between phosphate groups, in a thionoester, sulfur replaces the carbonyl oxygen in an ester. Such compounds are prepared by the reaction of the thioacyl chloride with an alcohol
The enzyme, released into the mouth along with the saliva, catalyzes the first reaction in the digestion of dietary lipid, with diglycerides being the primary reaction product. Lingual lipase, together with gastric lipase, comprise the two acidic lipases, lingual lipase uses a catalytic triad consisting of aspartic acid-203, histidine-257, and serine-144, to initiate the hydrolysis of a triglyceride into a diacylglyceride and a free fatty acid. First, there is a series of deprotonations that make the serine a better nucleophile, the lone pair on the oxygen of the serine undergoes a nucleophilic addition to either the first or the third carbonyl of the triacylglycerol. Next, the electrons that had moved to form the carbonyl transfer back down to reform the carbonyl, the diacylglycerol leaving group is protonated by His-257. Following another round of deprotonations, the pair on the oxygen of water undergoes a nucleophilic addition to the carbonyl that reformed in the previous step. The electrons that had moved up from the carbonyl come back down to reform it and kick off the Ser, the final products of the reaction are the conserved catalytic triad, a diacylglycerol and a free fatty acid.
Monoacylglyceride is present in a concentration and is produced following a second round of hydrolysis by the same mechanism. It acts on tryglicerides to help breakdown food as a part of saliva composition, patients with cystic fibrosis have an 85% chance of additionally experiencing the effects of exocrine pancreatic insufficiency. In the most extreme cases, these patients will produce no pancreatic lipase, yet even when the enzyme is completely absent, dietary fat is still absorbed. Studies have shown even in these cases, lingual lipase is present in normal amounts. This can be attributed to the fact that lingual lipase has a low pH optimum and can remain active through the stomach into the duodenum. The proposed mechanism of lingual lipase preferentially cleaving short and medium chain triacylglycerols provides a means for absorption without the need for micelle formation and chylomicrons. Short and medium chain fatty acids can be absorbed directly through the mucosal cells into the blood stream without further packaging.
In the uterus, the fetus is dependent on a high-carbohydrate diet, after birth, fat in mothers milk or a milk substitute becomes the major source of nutrition. Absorptive rates of fat are much lower in neonates than in adults, 65-80% as compared to >95% respectively. Furthermore, milk fat is not a substrate for pancreatic lipase. This enzyme activity has seen as early as 26 weeks gestational age
Pancreatic lipase family
Triglyceride lipases are a family of lipolytic enzymes that hydrolyse ester linkages of triglycerides. Lipases are widely distributed in animals and prokaryotes, at least three tissue-specific isozymes exist in higher vertebrates, pancreatic and gastric/lingual. These lipases are closely related to other and to lipoprotein lipase. The most conserved region in all these proteins is centred on a residue which has been shown to participate, with an histidine. Such a region is present in lipases of prokaryotic origin and in lecithin-cholesterol acyltransferase. Pancreatic lipase, known as pancreatic lipase, is an enzyme secreted from the pancreas. The resulting monomers are moved by way of peristalsis along the intestine to be absorbed into the lymphatic system by a specialized vessel called a lacteal. This protein belongs to the pancreatic lipase family, unlike some pancreatic enzymes that are activated by proteolytic cleavage, pancreatic lipase is secreted in its final form. However, it becomes efficient only in the presence of colipase in the duodenum, in humans, pancreatic lipase is encoded by the PNLIP gene.
LIPC LIPG LIPH LIPI LPL PLA1A PNLIP PNLIPRP1 PNLIPRP2 PNLIPRP3 Pancreatic lipase is secreted into the duodenum through the system of the pancreas. Its concentration in serum is normally very low, through measurement of serum concentration of pancreatic lipase, acute pancreatitis can be diagnosed. One peptide selected by phage display was found to inhibit pancreatic lipase, orlistat Roussel A, Yang Y, Ferrato F, Verger R, Cambillau C, Lowe M. Structure and activity of rat pancreatic lipase-related protein 2. Colipase residues Glu64 and Arg65 are essential for normal lipase-mediated fat digestion in the presence of bile salt micelles, freie AB, Ferrato F, Carrière F, Lowe ME. Val-407 and Ile-408 in the beta5-loop of pancreatic lipase mediate lipase-colipase interactions in the presence of bile salt micelles, hegele RA, Ramdath DD, Ban MR, Carruthers MN, Carrington CV, Cao H. Polymorphisms in PNLIP, encoding pancreatic lipase, and associations with metabolic traits. Chahinian H, Sias B, Carrière F, the C-terminal domain of pancreatic lipase and structural analogies with c2 domains.
Ranaldi S, Belle V, Woudstra M, Rodriguez J, Guigliarelli B, Sturgis J, Carriere F, lid opening and unfolding in human pancreatic lipase at low pH revealed by site-directed spin labeling EPR and FTIR spectroscopy. A scan of chromosome 10 identifies a novel locus showing strong association with late-onset Alzheimer disease, thomas A, Allouche M, Basyn F, Brasseur R, Kerfelec B. Role of the lid hydrophobicity pattern in pancreatic lipase activity, van Tilbeurgh H, Egloff MP, Martinez C, Rugani N, Verger R, Cambillau C