Acetyl esterases, function

Acetyl esterases, function, 430 N-Acetylglucosaminidases, function, 480 Acetyl xylan esterases, function, 430431,432r... 

Esters of cellulose with interesting properties such as bioactivity and thermal and dissolution behavior can be obtained by esterification of cellulose with nitric acid in the presence of sulfuric acid, phosphoric acid, or acetic acid. Commercially important cellulose esters are cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Cellulose esters of aliphatic, aromatic, bulky, and functionalized carboxylic acids can be synthesized through the activation of free acids in situ with tosyl chloride, iV,iV -carbonyldiimidazole, and iminium chloride under homogeneous acylation with DMA/LiCl or DMSO/TBAF. A wide range of cellulose esters that vary in their DS, various substituent distributions, and several desirable properties can be obtained through these reactions. Recently, a number of enzymes that degrade cellulose esters have been reported. Some of them are acetyl esterases, carbohydrate esterase (CE) family 1, and esterases of the CE 5 [169-172] family. 

The use of prodrugs with higher lipophrlicity compared to the parent molecule is realized in the classical example of heroin and morphine. Heroin, the di-acetyl derivative of morphine, penetrates the BBB by one log order better than morphine and is cleaved by tissue esterases to release the active parent drug. As follows from fhe pharmacokinetic principles shown in Section 2.3.2.1 (Eq. 2.3), brain concentration is a function of bofh BBB permeability, reflected by and plasma area under the curve ... 

CE 6 apparently contains only acetyl xylan esterases, but catalytic functions of many of the proteins in it have not been experimentally confirmed. One such protein from Arabidopsis thaliana proved to have a catalytic triad,and as isolated was found to have the catalytic serine covalently modified by PMSF. This enabled an oxyanion hole formed by two main-chain NH and a side-chain carboxamide to be identified. 

One of the main functions of sialic acid O-acetyl groups is their inhibitory effect on the action of both sialidases and sialic acid-specific lyases [5,33]. While a 4-O-acetyl group completely hinders the action of these enzymes (with the exception of a slow release by viral sialidases [252]), such ester groups at the sialic acid side chain appreciably hinder hydrolysis of the glycosidic bond of these sugars and their further breakdown by lyases. The existence of esterases acting on O-acetylated sialic acids prior to sialidase is therefore a prerequisite or at least supports the rapid turnover of O-acetylated sialoglycoconjugates. The possibility of the existence of such enzymes was raised by the observation that... 

Genetic factors are particularly important in humans and can influence the response to the compound or the disposition of the compound and hence its toxicity. Several genetic factors affecting metabolism are known in which a non-functional or less functional form of the enzyme is produced in a particular phenotype, e.g. acetylator phenotype (N-acetyltransferase NAT2) hydroxylator status (cytochrome P-450 2D6) esterase deficiency (pseudocholinesterase). 

The activity of these biofunctional peptides is based on their inherent amino acid composition and sequence. The size of active sequences may vary from 2 to 20 amino acid residues, and many peptides are known to have multifunctional properties [89], e.g., peptides from the sequence 60-70 of P-casein show immunostimulatory, opioid, and angiotensin I converting enzyme (acetyl choline esterase [ACE]) -inhibitory activities. This sequence has been defined as a strategic zone [90,91]. The sequence is protected from proteolysis because of its high hydrophobicity and the presence of proline residues. Other examples of the multi-functionality of milk-derived peptides include the... 

Klein A, Krishna M, Varki NM, Varki A (1994) 9-O-Acetylated sialic acids have widespread but selective expression analysis using a chimeric dual-function probe derived from influenza C hemagglutinin-esterase. Proc Natl Acad Sci USA 91 7782-7786... 

---