Enzymes groups oxidoreductases

The last enzymatic step of the cannabinoid pathway is the production of THCA (3.5), CBDA (3.4) or CBGA (3.6). The compounds are produced by three different enzymes. The first enzyme produces the major psychoactive compound of cannabis, THCA [21,38] the second and third are responsible for the production of CBDA [39] and CBGA [40], respectively. All of these enzymes belong to the enzyme group oxidoreductases [38-41], which means that they are able to use an electron donor for the transfer of an electron to an acceptor. From these enzymes only the THCA and the CBDA synthase gene sequence have been elucidated. Their product also represents the highest constituent in most C. sativa strains. 

Isolated oxidoreductases always depend on cofactors for the transfer of electrons. Enzyme groups which are well characterized with respect to their biochemistry are those requiring the nicotinamide coenzymes NAD or NADP, the flavins FAD or FMN and the ortho-quinoids such as pyrroloquinoline quinone (PQQ) or trihydroxy-phenylalanine (TOPA). 

Of the six main classes of enzymes, hydrolases, oxidoreductases and transferases have been the three most useful in kinetic resolution. Among the hydrolases, lipases are extensively used. The molecular machinery of lipases consists of a catalytic triad of the amino acids serine, histidine, and aspartic (or glutamic) acid. The enzyme first transfers the acyl group of an ester to the hydroxyl group of the serine residue to form the acylated enzyme. The acyl group is subsequently transferred to an external nucleophile with the return of the enzyme to its pre-acylated state to start the process again. A variety of nucleophiles can participate in this process water results in hydrolysis, an amine results in amidation, an alcohol results in esterification or transesterification, and hydrogen peroxide results in the formation of perac-id. Another reason which favored the relatively wide applicability of lipases in enzymatic... 

The application of the biocatalysts in this overview is limited to these stable enzymes, which do not need cofactors, such as the various hydrolytic enzymes, some lyases, transferases and isomerases. In addition to these groups, oxidoreductases, which demand NAD or NADP as cofactors, some pyridoxyl-phosphate dependent lyases with simple systems for cofactor regeration and finally, various aldolases in combination with L-glycerol- phosphate oxidase and catalase are useable to some extent in cell-free form. 

Biological oxidation is catalysed by a large group of enzymes called oxidoreductases (EC 1 611 enzymes total). Oxidation or reduction of a substrate can occur in a number of ways, as is shown in Table 1.1, where the distinction is made on the basis of electron acceptor (B, O2 or H2O2) and products formed. 

There has been a change over the last few years hydrolytic enzymes are no longer the most frequently used enzyme group in R D. Among the lectures and posters presented in 2013, oxidoreductases became the ciurent stars, followed by transferases. 

Enzymes are classified into six categories depending on the kind of reaction they catalyze, as shown in Table 26.2. Oxidoreductases catalyze oxidations and reductions hansferases catalyze the transfer of a group from one substrate to another hydrolases catalyze hydrolysis reactions of esters, amides, and related substrates lyases catalyze the elimination or addition of a small molecule such as H2O from or to a substrate isomerases catalyze isomerizalions and ligases catalyze the bonding together of two molecules, often coupled with the hydrolysis... 

The oxidation by strains of Pseudomonas putida of the methyl group in arenes containing a hydroxyl group in the para position is, however, carried out by a different mechanism. The initial step is dehydrogenation to a quinone methide followed by hydration (hydroxylation) to the benzyl alcohol (Hopper 1976) (Figure 3.7). The reaction with 4-ethylphenol is partially stereospecific (Mclntire et al. 1984), and the enzymes that catalyze the first two steps are flavocytochromes (Mclntire et al. 1985). The role of formal hydroxylation in the degradation of azaarenes is discussed in the section on oxidoreductases (hydroxylases). 

The first test case was the ferrous high-spin state (Fe, S = 2) in the picket-fence porphyrin acetate complex [Fe(CH3COO)(TPpivP)] [13, 23], which is a model for the prosthetic group termed P460 of the multiheme enzyme hydroxyl-amine oxidoreductase from the bacterium Nitrosomonas europeae. Both the picket-fence porphyrin and the protein P460 exhibit an extraordinarily large quadrupole splitting, as observed by conventional Mossbauer studies [56]. 

Mammalian thioredoxin reductases are a family of selenium-containing pyridine nucleotide-disulfide oxidoreductases. These enzymes catalyze NADPH-dependent reduction of the redox protein thioredoxin (Trx), which contains a redox-active disulfide and dithiol group and by itself may function as an efficient cytosolic antioxidant [77]. One of the functions of Trx/ thioredoxin reductase system is the NADPH-catalyzed reduction of protein disulfide [78] ... 

We have already seen the diversity of function in the lyases, hydrolases and oxidoreductases. Several other types of zinc coordination are found in a number of other enzymes, illustrated in Figure 12.8. These include enzymes with the coordination motif [(His)2(Cys) Zn2+-OH2], illustrated by the lysozyme of bacteriophage T7 this group also includes a peptidyl deformylase. 

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