Phenolase

Copper is one of the twenty-seven elements known to be essential to humans (69—72) (see Mineral nutrients). The daily recommended requirement for humans is 2.5—5.0 mg (73). Copper is probably second only to iron as an oxidation catalyst and oxygen carrier in humans (74). It is present in many proteins, such as hemocyanin [9013-32-3] galactose oxidase [9028-79-9] ceruloplasmin [9031 -37-2] dopamine -hydroxylase, monoamine oxidase [9001-66-5] superoxide dismutase [9054-89-17, and phenolase (75,76). Copper aids in photosynthesis and other oxidative processes in plants. 

Amylase, invertase, peroxida,se, phenolase, phosphatases, polygalacturonase, protea.se Flavonones and nucleotides... 

This copper-dependent enzyme [EC 1.14.18.1] (also known as tyrosinase, phenolase, monophenol oxidase, and cresolase) catalyzes the reaction of L-tyrosine with L-dopa and dioxygen to produce L-dopa, dopaquinone, and water. This classification actually represents a set of copper proteins that also catalyze the reaction of catechol oxidase [EC 1.10.3.1] if only 1,2-benzenediols are available as substrates. 

The products of oxidation are easily visualized shortly after ozone treatments but no claim should be made that phenolics or the oxidative enzymes, polyphenol oxidase, phenolase or peroxidase... 

The involvement of phenols and enzymes of the phenolase complex appears to be secondary to the induction of necrosis. The induction must involve a modification of membrane structure which leads to altered membrane permeability and loss of cell compart-mentalization. If this occurs, regulation of cellular metabolism is lost, enz3mies are activated, and these and their substrates that are normally separated by membranes would react together. 

Phenols are present in chloroplasts (23, 24) and in vacuoles (25) of plant cells. The enzyme polyphenol oxidase and other enzymes of the phenolase complex are bound to the chloroplast lamellae or stroma 27) and in the cytoplasm (26). Although... 

Mason (30) and Pierpoint (31) have described the involvement of o-diphenols in plants and how they contribute to abnormal plant pigmentation. o-Diphenols are oxidized to o-quinones by enzymes of the phenolase complex (o-diphenol O2 oxidoreductase, E.C. 1.10.3.1) and by peroxidase (E.C. 1.11.1.7). o-Quinones react with amino acids, proteins, amines and thiol groups of proteins to polymerize and from reddish-brown pigments. Concentrations of caffeic acid are doubled in both bean (8) and peanut... 

Fukuzumi and Itoh have jointly reported on a if-peroxo dicop-per(ll) complex that acts as a functional model for the phenolase activity of tyrosinase. lithium salts of para-substituted phenols were used as substrates, reaching yields between 60 and 90% with only the catechol product formed... 

In 1955, two types of oxygenases were independently discovered by two groups of investigators. Mason and his collaborators found that during the oxidation of 3,4-dimethylphenol to dimethylcatechol by phenolase, the oxygen atom incorporated into the substrate was derived exclusively from molecular oxygen2 [Eq. (1)]. 

As in the cases of phenolase and pyrocatechase, respectively, oxygenases catalyze the incorporation of either one or two atoms of molecular oxygen into their substrates. Therefore, they are classified into two major groups, monooxygenases and dioxygenases1S). 

Morphine and codeine biosynthesis (Samuelsson, 1999 Herbert et al., 2000 Novak et al., 2000) Studies on the biosynthesis of morphine have been carried out mainly on cell cultures mainly of Coptis japonica and species of Thalictrum. Two enzymes (tyrosine decarboxylase and phenolase) catalyze the formation of dopamine from one molecule tyrosine. Dopamine is also the key intermediate in the biosynthesis of mescaline. 

Table II. Consumption of Oxygen after Adding Amino Acids to the System Phenolase—Catechol (1,2-Dihydroxybenzene)...

PPO (known also as catecol oxidase, phenolase or diphenol-oxygen oxidereductase) and POD catalyse the oxidation of o-diphenols to o-diquinones, as in the hydroxylation of monophenols [13]. PPO is located exclusively in the plastids of healthy tissues, while most phenolic compounds are localized in the vacuoles, the two compounds thus being physically separated [13]. 

Phenolase -fromtoluene [HYDROCARBON OXIDATION] (Vol 13) -use m clinical assay [AUTOMATED INSTRUMENTATION - CLINICAL CHEMISTRY] (Vol 3) -copperm [COPPERCOMPOUNDS] (Vol7)... 

Cu Lactase, phenolase. tyrosinase, uricise Ceruloplasmin, cytochrome... 

Studies on irradiated solutions of phenolase showed that the enzyme was inactivated. The radiation-induced changes were found to be different from those reported to occur upon denaturation of proteins. Infrared absorption spectra revealed that deamination had occurred. Acid- and basebinding groups were reduced in number rather than increased, and the optical rotation became more dextrorotatory than levorotatory. It was fur-... 

The presence of oxygen was shown to enhance inactivation of the enzyme, while the presence of ovalbumin in the phenolase solution protected the activity. This was accepted as evidence that indirect action of the radiation was responsible for the inactivation of phenolase since the presence of dissolved oxygen or protein would have no effect on direct collisions of the 7-rays and the enzyme molecules. 

The liberation of sulfhydryl groups was not detected after irradiation of 0.5% ovalbumin solutions. Since it was shown that the presence of inert protein protected, rather than inactivated, phenolase, it was concluded that thiol groups, produced by disruption of disulfide bonds in the protein, had no significant role in phenolase inactivation. 

Reports indicated that the phenolase responsible for melanogenesis of shrimp was located in the shell and concentrated primarily at the joints between segments. It was concluded that water and oxygen may diffuse through these joints, and that their radiolysis products were responsible for the inactivation of phenolase and subsequent reduction of melanosis. 

This class includes enzymes that use diphenols or related compounds as electron donors and oxygen as the acceptor, thereby forming the oxidized donor and water. Members include catechol oxidase (E.C. 1.10.3.1), laccase (E.C. 1.10.3.2), and o-aminophenol oxidase (E.C. 1.10.3.4). Laccase is also known as / -diphenoloxidase. whereas catechol oxidase is also known as diphenoloxidase, phenoloxidase, polyphenoloxidase, o-diphenolase, phenolase and tyrosinase. Many of these names are also used in reference to a different enzyme, monophenol monooxygenase (E.C. 1.14.18.1). This enzyme will be discussed further in Section 1.8.2.2. 

The phenol oxidases probably play no important role in the elimination of phenolic pressor amines, in spite of the importance that has been attached to the oxidation of the catechol nucleus in the past. The names phenolase and cresolase, polyphenol oxidase, and catechol oxidase serve to identify the enzyme with its mono- or diphenolic substrate, but they usually occur together and are difficultly separated. The enzymes have been purified and their characteristics have been described (56, 104, 106, 156). Beyer (21), Alles (5), and Randall and Hitchings (129) have described the relationship of structure of the phenolic pressor amines to the rate of oxidation of their nucleus in the presence of these enzymes. 

Pharmaceutical 53 analysis 79 formulations el57 Phenanthrene 522 Phenol 211, 362, el63 Phenolase 371... 

Martin, J. P., and Haider, K. (1979). Biodegradation of 14C-labeled model and cornstalk lignins, phenols, model phenolase humic polymers, and fungal melanins as influenced by a readily available carbon source and soil. Appl. Environ. Microbiol. 38, 283-289. 

This forms the tough, outer layer of the egg. It consists largely of protein, the precise composition of which is uncertain. The reported absence of phenol or phenolase indicates that it is not the tanned protein sclerotin (440,640),... 

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