Thio esterase

Modulation of the quantity and/or quality of poly(3HAMCL) synthesized in peroxisomes was also achieved by modifying the endogenous fatty acid biosynthetic pathway [58]. For example, expression of the peroxisomal PHA synthase in an A. thaliana mutant deficient in the synthesis of triunsaturated fatty acids [59] resulted in the synthesis of a PHA having an almost complete absence of triunsaturated 3-hydroxyacid monomers [58]. In a different strategy, expression of a fatty acyl-ACP thio esterase in the plastid was combined with the expression of a peroxisomal PHA synthase [58]. Fatty acyl-ACP thioesterases are... 

In the biosynthesis of most anthracychnes, the first polyketide imit is a propionate instead of acetate two enzymes, a ketosynthase [3] and a thio-esterase [4], cause the addition of a propionyl unit from propionyl-CoA as the first unit of the polyketide chain. This results in being an ethyl group. 

Infantile neuronal ceroid lipofuscinosis (CLNl) Palmitoyl protein thio-esterase 1 (PPTl) lp32 256730... 

Comprehensive Biological Catalysis—a Mechanistic Reference Volume has recently been published. The fiiU contents list (approximate number of references in parentheses) is as follows S-adenosylmethionine-dependent methyltransferases (110) prenyl transfer and the enzymes of terpenoid and steroid biosynthesis (330) glycosyl transfer (800) mechanism of folate-requiring enzymes in one-carbon metabohsm (260) hydride and alkyl group shifts in the reactions of aldehydes and ketones (150) phosphoenolpyruvate as an electrophile carboxyvinyl transfer reactions (140) physical organic chemistry of acyl transfer reactions (220) catalytic mechanisms of the aspartic proteinases (90) the serine proteinases (135) cysteine proteinases (350) zinc proteinases (200) esterases and lipases (160) reactions of carbon at the carbon dioxide level of oxidation (390) transfer of the POj group (230) phosphate diesterases and triesterases (160) ribozymes (70) catalysis of tRNA aminoacylation by class I and class II aminoacyl-tRNA synthetases (220) thio-disulfide exchange of divalent sulfirr (150) and sulfotransferases (50). 

Advantage of species differences in metabolism was taken with the synthesis of malathion which is attacked by esterases in mammals and excreted rapidly as the diacid before conversion of the innocuous thio-phosphate to the toxic phosphate. Insects have very low levels of esterases, and metabolism to the lethal oxo metabolite can occur unimpeded (Figure 20). 

Figure 8.14 Colourimetric assay. Acetyl Choline Esterase (AChE) assay system involving thio-acetylcholine that is hydrolyzed to thio-choline. This in turn combines with colourless reagent 5,5 -dithio-bis(nitrobenzoic acid) (DTNB) to form yellow coloured 5-thio-2-nitro-benzoic acid (TNB).

Regioselectively protected cytidine derivatives have been prepared from the peracetylated nucleoside using lipase and esterase reactions. There have been reports on the use of bacterial proteases for the selective acylation of sucrose to produce a variety of different acyl and acrylate esters. 8-Aminooctyl 5-5-coniferyl-5-thio-a-L-arabinofuranoside(27) attached to sepharose proved to be a selective affinity ligand for feruloyl esterase A. niger ... 

C. Hydrolysis A wide range of esterases exist for the hydrolysis of compounds. Examples include (a) carboxylesterases (EC 3.1.1.1) (b) amidases (EC 3.5.1.4 and others) (c) phosphatases (EC 3.1.3.1, 3.1.3.2 and others) Esters, amides, hydrazides and carbonates Thio-orga nophosphate Single or multiple end-products can be produced by hydrolysis depending on the enzymes involved and the substrate of the reaction, ... 

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