Biochemical oxidations hydroxylation

Xanthophylls are the main carotenoids of plants. They primarily arise as products of biochemical oxidation (hydroxylation and epoxidation) of carotenes. Xanthophylls derived from acyclic carotenes occur in foods in small quantities. For example, tomatoes contain as minor pigments 1,2-epoxylycopene, 5,6-epoxylycopene, 1,2-epoxyphytoene and some other compounds. Much more common are monohydroxysubstituted alicyclic derivatives of carotenes called cryptoxanthins. Most plant materials contain small amounts of a-cryptoxanthin also called zeinoxanthin, derived from a-carotene (9-182) and P-cryptoxanthin, derived from... 

Periodic acid oxidation has proved to be a very useful tool in enzymology since a wide variety of biochemicals contain hydroxyl groups on adjacent carbon atoms. For example, periodate-oxidized ATP (also called adenosine 5 -triphosphate 2, 3 -dialdehyde) has often been used as an alternative substrate or an irreversible inhibitor for a wide variety of ATP-utilizing enzymes. This compound, and many others, are now commercially available, even though they are readily synthesized e.g., periodic acid oxidized ADP, AMP, adenosine, P, P -di(adenosine-5 )pentaphosphate, P, P -di(adenosine-5 )tetraphos-phate, GTP, GDP, GMP, guanosine, CTP, CDP, CMP, etc. In the case of the nucleosides, commercial sources also can supply the dialcohol form of the nucleoside i.e., the nucleoside has first been oxidized with periodic acid and then reduced to the dialcohol with borohydride. 

The first step in oxidation of alkanes is usually an 02-requiring hydroxylation (Chapter 18) to a primary alcohol. Further oxidation of the alcohol to an acyl-CoA derivative, presumably via the aldehyde (Eq. 17-2), is a frequently encountered biochemical oxidation sequence. 

Enantioselective hydroxylation of double bonds also occurs in biochemical oxidation by Pseudomonas putida [1073]. 

Secondary steroidal alcohols react in preference to primary allylic alcohols in biochemical oxidations usingJihizopus arrhizus and Helicostylum piriforme or Cunninghamella blakesleeana. However, the reaction is complicated by hydroxylations in positions 6 (with Rhizopus arrhizus) and 9 (with Helicostylum piriforme or Cunninghamella blakesleeana) [1059]. 

Biochemical oxidations of sugars are very common and versatile. Depending on the microorganism used, hydroxylic groups in various positions can be oxidized to keto groups, and the aldehyde group is converted into a carboxyl group. 

One important application is in the field of carbohydrate transformations, the catalytic oxidation of D-glucose to D-gluconic acid represents an economically competitive route with respect to biochemical oxidation [4], This new process is the result of extensive studies on the selective Cl-hydroxyl group oxidation in the presence of O2 using a Pt or Pd catalyst modified with cocatalysts [5]. 

It has been observed that the metabolism of tryptophan is also greatly influenced by riboflavin deficiency. In this deficiency there is an increased excretion of metabolic products of tryptophan such as N -acetylkynurenine, N -acetyl-3-hydroxy-kynurenine, kynurenic acid, and xanthurenic acid. In a search for the specific metabolic defect Charconnet-Harding, Dalgliesh, and Neuberger Biochem. J. London) 63, 513, 1953) concluded that riboflavin might be concerned with an unknown phosphorylation step but is not concerned with the oxidative hydroxyl-ation of kynurenine to hydroxykynurenine or anthranilic acid to hydroxyanthranilic acid. The authors also point out that riboflavin may have no specific metabolic role in tryptophan metabolism. 

The fact that alkanes are oxidized suggested that atomic oxygen is liberated and also the attack on aromatic hydrocarbons " seems to differ from reaction via hydroxyl radicals. Actually, the hydroxy-lation of aromatics by this path has been considered as a model for biochemical oxidation. 

Identification, isolation, and removal of (polyhydroxy)benzenes from the environment have received increased attention throughout the 1980s and 1990s. The biochemical activity of the benzenepolyols is at least in part based on thek oxidation—reduction potential. Many biochemical studies of these compounds have been made, eg, of enzymic glycoside formation, enzymic hydroxylation and oxidation, biological interactions with biochemically important compounds such as the catecholamines, and humic acid formation. The range of biochemical function of these compounds and thek derivatives is not yet fully understood. 

It was subsequently discovered that lucanthone is metabolized in the body in part to hycanthone (30), a compound with enhanced schistomacidal activity. The relatively high biologic activity of lucanthone in experimental animals compared to man was subsequently attributed to the inefficient hydroxylating system present in man for this biochemical conversion.Microbiologic oxidation of lucanthone by fermentation with the fungus Aspergil-lus scelorotium affords hycanthone. ... 

BUTTERFIELD D A, MARINA A, JAROSLAW K, ANTONIO s (2002) FeruUc add antioxidant protection against hydroxyl and peroxyl radical oxidation in synaptosomal and neuronal cell culture systems in vitro Structure activity studies. JNutri Biochem, 13(5) 273-81. 

Van Zyl JM, BJ van der Walt (1994) Apparent hydroxyl radical generation without transition metal catalysts and tyrosine nitration during oxidation of the anti-tubercular drug, isonicotinic acid hydrazide. Biochem Pharmacol 48 2033-2042. 

Hunt, J.V., Dean, R.T. and Wolff, S. (1988). Hydroxyl radical production and autoxidative glycosylation. Glucose oxidation as the cause of protein damage in the experimental glycation model of diabetes mellitus and ageing. Biochem. J. 256, 205-212. 

Klein, S.M., Cohen, G., Lieber, C.S. and Cederbaum, A.l. (1983). Increased microsomal oxidation of hydroxyl scavenging agents and ethanol after chronic consumption of ethanol. Arch. Biochem. Biophys. 223, 425-432. 

Fukuzawa, K. Gebicki, J. M. Oxidation of alpha-tocopherol in micelles and liposomes by the hydroxyl, perhydroxyl, and superoxide free radicals. Arch. Biochem. Biophys. 1983, 226, 242-251. 

The marine environment acts as a sink for a large proportion of polyaromatic hydrocarbons (PAH) and these compounds have become a major area of interest in aquatic toxicology. Mixed function oxidases (MFO) are a class of microsomal enzymes involved in oxidative transformation, the primary biochemical process in hydrocarbon detoxification as well as mutagen-carcinogen activation (1,2). The reactions carried out by these enzymes are mediated by multiple forms of cytochrome P-450 which controls the substrate specificity of the system (3). One class of MFO, the aromatic hydrocarbon hydroxylases (AHH), has received considerable attention in relation to their role in hydrocarbon hydroxylation. AHH are found in various species of fish (4) and although limited data is available it appears that these enzymes may be present in a variety of aquatic animals (5,6,7,8). 

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