Enzyme grouping

Some of the major enzyme groups that facilitate this transformation are heme-containing MOs of the cytochrome P450 type [111], alkane hydroxylases, xylene monooxygenases, styrene monooxygenases [105], and haloperoxidases [112],... 

Type of Enzyme Group Organism Halogen Reference... 

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. 

We may note, parenthetically, that a somewhat similar possibility exists for the enzyme group in which the cofactor is pyridoxal phosphate... 

Within the NiFe(Se) hydrogenase family, the unrooted tree (Fig. 2.4) clearly reveals several major lineages. As might be expected, the enzyme groups discussed above all emerge as distinct clades which reflect the major prokaryotic groups and the enzyme... 

The enzymes grouped in this section are biologically very distinct. Lip, by definition, catalyzes the hydrolysis of one or more of the three ester bonds linking fatty acids to the hydroxyl positions of glycerol (Equation (6)). 

Only the enzymes mentioned in this atlas are listed here, from among the more than 2000 enzymes known. The enzyme names are based on the iUBlVlB s of dal Enzyme nomenclature 1992. The additions shown in round brackets belong to the enzyme name, while prosthetic groups and other cofactors are enclosed in square brackets. Common names of enzyme groups are given in italics, and trivial names are shown in quotation marks. 

In these derivatives, nucleophilic attack at the anomeric carbon atom should be greatly facilitated if the negative charges on oxygen atoms of the pyrophosphate group are removed. In consequence, intermediates such as 121, where R1 = nucleoside, and R2 = hydrogen atoms or electrophilic enzyme groups, are probable intermediates in these reactions. 

This paper is a contribution from the Oxford Enzyme Group and we wish to acknowledge the help of very many members of that group. 

Figure 14-11 Schematic diagram of the active site of the pyruvoyl enzyme histidine decarboxylase showing key polar interactions between the pyruvoyl group and groups of the inhibitor O-methylhistidine and surrounding enzyme groups. Aspartate 63 appears to form an ion pair with the imidazolium group of the substrate.268 Hydrogen bonds are indicated by dotted lines. See Gallagher et al.269...

Nucleophilic addition of an enzyme group results in irreversible inhibition ... 

Enzyme Group that Combines with Inhibitor... 

The range of catalytic proficiencies for enzymes suggests that there are features of catalysis in enzymes that involve factors other than stabilization of transition states. One important distinction is that the enzyme active site contains catalytic groups that are able to access reactive intermediates, while intermediates formed in solution have lifetimes that are less than the time needed for a reagent to diffuse to the site of the reaction.33 In the enzyme, groups are initially associated with the bound substrate in a specific array and continue to be available through the course of the reaction. Diffusional introduction of catalytic groups is overcome by pre-association of the catalysts and reactant prior to the formation of any reactive intermediate. This accesses modes of catalysis that are not possible if the catalyst and intermediate must become associated after the intermediate has formed. 

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). 

The molybdenum and tungsten centers are classified by the coordination of their MVI states and sorted into enzyme groups based on protein sequence homology. There are four distinct subfamilies of enzymes, which are based on... 

Four major enzyme groups are secreted lipolytic, proteolytic, amylolytic, and nucleic acid splitting enzymes. These pancreatic enzymes, some of which are secreted in multipile forms, possess specificities complementary to die intestinal membrane-bound enzymes (Tabic 1). Fresh, uncontsnkinated pancreatic juice is without proteolytic activity because these enzymes am in the form of inactive zymogens. An important fraction of the calcium in pancreatic juice accompanies the enzymes, especially ct-amylase. Human pancreatic juice is moat dose to that of the pig, with high proportions of lipase and a-amylase in comparison with other mammals [1]. Therefore, pig pancreas extract, pancreatin, has up to now been die oreferred enzvme source for therapeutic tuncreas substitution. 

Fig. 8-2 Binding of the substrate (NAG-NAM)3 to the active site of lysozyme. The substrate is drawn with bold bonds, the enzyme groups with light-face bonds. H bonds are indicated by dotted lines.

The enzyme activity is widely distributed in bacteria, yeasts, plants, and animals, and catalyzed by at least live structurally distinct enzyme groups (Takaha and Smith, 1999) as shown in Table 28.3. In addition to the inter-molecular trans-glycosylation reaction expressed in equation (4), 4aGT also catalyze the intramolecular transglycosylation reaction (cyclization reaction) of a-1,4 glucan to produce cyclic a-1,4 glucan as shown in equation 28.5 ... 

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