Hydrolyzable ester bonds

All purified poly(HA) depolymerases are specific for either poly(HASCL) or poly(HAMCL). Even a poly(3HB) depolymerase of S. exfoliatus K10, a strain that degrades both poly(3HB) and poly(3HO), is specific for poly(HASCL) [49]) indicating at least one additional depolymerase with specificity for poly(HAMCL) in S. exfoliatus. Experiments with copolymers consisting of 3-hydroxybutyrate and 3-hydroxyhexanoate and A.faecalis T1 poly(3HB) depolymerase are in agreement with the results obtained with poly(HASCL) and poly(HAMCL) the depolymerase was not able to hydrolyze ester bonds between two 3HAMCL monomers and between 3-hydroxybutyrate and 3-hydroxyhexanoate [50]. 

Hydrolysis of Copolyamide-esters (CPAEs) by Lipase (jj,). CPAEs were synthesized by the amide-ester interchange reaction between polyamide and polyester. The length of the polyamide blocks was measured after hydrolysis of ester bonds in CPAE by alkali at 30 C. The infrared spectra after hydrolyzing ester bonds on CPAEs showed that the ester bonds were almost completely removed. The molecular weight distribution of polyamide blocks was examined by GPC (Table II). The following samples were used CPAE-1 (reaction time for synthesis, 1 hr) and CPAE-2 (reaction time, U hr) composed of nylon 6 and PCL at a 50/50 molar ratio, CPAE-3 (reaction time, 1 hr) and CPAE-U (reaction time,... 

Hydrolases, which catalyze the hydrolysis of various bonds. The best-known subcategory of hydrolases are the lipases, which hydrolyze ester bonds. In the example of human pancreatic lipase, which is the main enzyme responsible for breaking down fats in the human digestive system, a lipase acts to convert triglyceride substrates found in oils from food to monoglycerides and free fatty acids. In the chemical industry, lipases are also used, for instance, to catalyze the —C N —CONH2 reaction, for the synthesis of acrylamide from acrylonitril, or nicotinic acid from 3-pyridylnitrile. 

Complex tannins are defined as tannins in which a catechin unit (1.39) is bound glycosidically to either a gallotannin or an ellagitannin unit. As the name implies, the structure of these compounds can be very complex. An example is Acutissimin A (1.99). This is a flavogallonyl unit bound glucosidically to Cl, with an additional three hydrolyzable ester bonds to a D-glucose-derived open-chain polyol. 

Various efficient polymers bearing hydrolyzable ester bonds, which degrade in a time dependent manner, have been designed. The linkages connect monomers either integrated in the polymer backbone or as cross-linking agents. Such... 

Fig. 3 Hydrolyzable, acid-sensitive and reducible bonds. Efficient and biocompatible high molecular weight polymers are created by reversible linkage of small molecular weight compounds. Thus, programmed biodegradation due to, for example, hydrolyzable ester bonds [92] (a), acid-sensitive ketal (b) or acetal linkages (c) [98] is possible. The reducing cytosolic environment can also be taken advantage of in order to create biodegradable polymers by introduction of disulfide bonds as shown in (d) [105, 106]...

Teomim et al. [406] reported the synthesis of ricinoleic acid and hydrogenated ricinoleic acid (hydroxystearic acid)-based monomers, which were synthesized from the attachment of a carboxylic acid side chain via a hydrolyzable ester bond to the hydroxy group (succinic acid/maleic acid). These monomers were... 

Samples 1 and 2 of Table 5 were hydrolyzed (ester bonds joining the polyether chain with the initiator) after hydrolysis the DP value measured by osmometry was half of that measured before hydrolysis. 

Lipases play the specific role of forming and hydrolyzing ester bonds involving long-chain carboxylic. 

Continuous assays are rarely described for lipases, but are frequently described for esterases. Similar to lipases, esterases hydrolyze ester bonds. However, in contrast to lipases, their substrates are water-soluble and thus water-soluble fluorescent substrates can be used to measure their enzymatic activity. Some of these water-soluble substrates have been proposed for the measurement of lipolytic ac-... 

Carboxypeptidase A has esterase activity as well as peptidase activity. In other words, the compound can hydrolyze ester bonds as well as peptide bonds. When carboxypeptidase A hydrolyzes ester bonds, Glu 270 acts as a nucleophilic catalyst instead of a general-base catalyst. Propose a mechanism for the carboxypeptidase A-catalyzed hydrolysis of an ester bond. 

Introduction - Phospholipases hydrolyze ester bonds in glycerophospho-lipids, and are readily subdivided according to the particular bond being attacked (Fig. 1). Hydrolysis of the fatty acylester bond is catalyzed by phospholipases of the A-type.1-3 Removal of the fatty acid at the sn l-position is produced by phospholipase Ai (EC 3.1.1.32) while removal of the fatty acid at the sn-2-position is due to phospholipase A2 (EC 3.1.1. ). Both phospholipases induce the formation of a lysophospholipld. The subsequent hydrolysis of the fatty acylester bond in lysophosphollplds is catalyzed by lysophospholipases (EC 3.4,1.5), which are now recognized as phospholipases of the B type.1-3... 

In order to carry out PHA production from triglycerides, the cells need to hydrolyze the triglycerides into free fatty acids that can be transported into the cells. For this, the cells need to secrete an enzyme called lipase. A wide variety of organisms is known to secrete lipolytic enzymes, mainly for lipid metabolism and signal transduction. Lipolytic enzymes can be classified into different classes, including lipases, esterases, and phospholipases (Arpigny and Jaeger 1999). Esterases are enzymes that hydrolyze ester bonds of soluble or partially soluble molecules. 

We synthesised different model polyesters and also oligomeric esters with specific structures to study the correlation between biodegiadability and the polymer-parameters responsible for the biological susceptibility. Polyesters are a suitable substance class for such investigations, because they can easily be synthesised in the lab, are potentially biodegradable due to their hydrolyzable ester bonds and they are of practical relevance, because most of the biodegradable plastics currently on the market are based on polyesters. A substantial part of our investigations is the detailed analysis of the structures of complex polyesters (e.g. copolyesters). 

An important group of enzymatically derived polymers is polyesters. In nature, they hold the fourth place after the three major biomacromolecules (nucleic acids, proteins, and polysaccharides). Important polyesters are poly(ethylene terephthalate) (PET), poly(butylene succinate) (PBS), poly(e-caprolactone) (poly(e-CL)), and poly(lactic acid) (PLA) (see Fig. 3.40). The former two are industrially produced via polycondensation and the latter two via ROP. Additionally, enzymes can be used to hydrolyze ester bonds, which offers the possibility to recycle commercially used materials, for example, PET [52]. 

The hydrolytic degradation behavior of the materials was tested in buffer solution pH 7 at 37 C. It was shown that the pol5mers are completely degradable and their degradation rate can be adjusted by the concentration of easily hydrolyzable ester bonds. 

Poly(Propylene Fumarate) (PPF) is a linear, unsaturated, hydrophobic polyester (Structure 12) containing hydrolyzable ester bonds along its backbone. PPF is highly viscous at room temperature and is soluble in chloroform, methylene chloride, tetrahydrofuran, acetone, alcohol, and ethyl acetate [66]. The double bonds of PPF can form chemical crosslinks with various monomers, such as W-vinyl pyrrolidone, poly(ethylene glycol)-dimethacrylate, PPF-diacrylate (PPF-DA), and diethyl fumarate [67,68]. The choice of monomer and radical initiator directly influence the degradative and mechanical properties of the crosslinked polymer. Once crosslinked, PPF forms a solid material with mechanical properties suitable for a range of bone engineering applications. 

Figure 2.36 Synthetic route of acrylate-urethane coating polymer with hydrolyzable ester bonds for salicylic acid release.

N-tosyl-L-phenylalanine ethyl ester (Formula 2.18) is a suitable substrate for the proteinase chymotrypsin which hydrolyzes ester bonds. When the ethoxy group is replaced by a chloro-methyl group, an inhibitor whose structure is similar to the substrate is formed (Na-tosyl-L-phenylalanine chloromethylketone, TPCK). 

Metabolites, in particular enzymes from bacteria and mold, attack the polymer skeleton, but more importantly the additives in the plastic material. Enzymes such as pepsin, trypsin, and chymotrypsin cleave the peptide bond in proteins and polyamides and can also hydrolyze ester bonds [32]. Their catalytic effect can activate hydrogen in the polymer chain, resulting in the formation of free radicals. The results of these processes are destroyed surfaces (Figure 5.371), loss of gloss, and changes in mechanical and electrical properties. 

Hydrolases Hydrolysis reactions Proteases hydrolyze peptide bonds in proteins. Lipases hydrolyze ester bonds in lipids. Carbohydrases hydrolyze glycosidic bonds in carbohydrates. Phosphatases hydrolyze phosphoester bonds. Nucleases hydrolyze nucleic acids. 

Lipases can be divided into three classes based on their specificity and/or selectivity regio- or positional specific lipases, fatty acid—type specific lipases, and specific lipases for a certain class of acylglycerols (mono-, di-, or triglycerides). In terms of regioselectivity, lipases have been divided into three types sn-1,3-specific (hydrolyze ester bonds in positions R1 or R3), sn-2-specific (hydrolyze ester bond in position R2), and nonspecific (do not distinguish between positions of ester bonds to be cleaved). Most known lipases are 1,3-regiospecific with activity on terminal positions. 

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