8’-Hydroxylating activity

Nothing is known about the identity of the iron species responsible for dehydrogenation of the substrate. Iron-oxo species such as FeIV=0 or Fem-OOH are postulated as the oxidants in most heme or non-heme iron oxygenases. It has to be considered that any mechanistic model proposed must account not only for the observed stereochemistry but also for the lack of hydroxylation activity and its inability to convert the olefinic substrate. Furthermore, no HppE sequence homo-logue is to be found in protein databases. Further studies should shed more light on the mechanism with which this unique enzyme operates. 

Steiner, U., Schhemann, W., and Strack, D., Assay for tyrosine hydroxylation activity of tyrosinase from betalain-forming plants and cell cultures, Anal. Biochem., 238, 72, 1996. 

Cytochrome P450 hydroxylation activity is well established in eukaryotic yeasts and some fungi,... 

Golbeck JH, SA Albaugh, R Radmer (1983) Metabolism of biphenyl by Aspergillus toxicarius induction of hydroxylating activity and accumulation of water-soluble conjugates. J Bacteriol 156 49-57. 

Inoue, K. et al. (1997). Relationship between CYP2C9 and 2C19 genotypes and tolbutamide methyl hydroxylation and S-mephenytoin 4 -hydroxylation activities in livers of Japanese and Caucasian populations. Pharmacogenetics, 7, 103-13. 

Influence of textural properties of TS-1 samples on phenol hydroxylation activity... 

In 1975, Hendrickson and Schwartzman reported a different mode of phosphorus-based hydroxyl activation using bis(phosphonium) electrophiles (R3P—O—PR3)2+. These highly reactive electrophiles are generated from the reagent combination of phosphine oxide and trifluoromethanesulfonic (triflic) anhydride [96]. Mukaiyama... 

He P, Court MH, Greenblatt DJ, et al. Factors influencing midazolam hydroxylation activity in human liver microsomes. Drug Metab Dispos 2006 34(7) 1198-1207. 

Figure 15.2 Improvement of the hydroxylation activity and enantioselectivity with Sphingomonas sp. HXN-200 hy substrate modification.

Bylund J, Kunz T, Valmsen K, Oliw EH. 1998. Cytochromes P450 with bisallylic hydroxylation activity on arachidonic and linoleic acids studied with human recombinant enzymes and with human and rat liver microsomes. J Pharmacol Exp Ther 284 51-60. 

Martinez C, Gervasini G, Agundez JA, Carrillo JA, Ramos SI, et al. 2000. Modulation of midazolam 1-hydroxylation activity in vitro by neurotransmitters and precursors. Eur J Clin Pharmacol 56 145-151. 

L-Asp hydroxylated at the /3-carbon to generate 7a ro-3-hydroxyl-L-aspartic acid has so far only been detected in cinnamycin and the duramycins, lantibiotics produced by actinomycetes. " This modification has also been found in mammalian proteins, such as the vitamin K-dependent protein C, and the epidermal growth factor (EGF)-like domain in human plasma factor IX. Both bovine and human aspartyl-/3-hydroxylases have been purified and characterized and their in vitro hydroxylation activity has been shown using proteins... 

Enzymatic hydroxylation activation has perhaps the highest potential of all enzyme-catalyzed transformations for synthetic applications. Currently, whole-cell processes are used and the outcomes are often unpredictable. The discovery of new oxygenases and efficient hosts for protein expression remain keys to further expanding the synthetic applications of biocatalytic C—H activation [89, 90]. 

The major pathway of coumarin metabolism in most human subjects is 7-hydroxyl-ation to form 7-hydroxy coumarin, which is excreted in the urine as both glucuronic acid and sulfate conjugates. Coumarin 7-hydroxylation activity exhibits a Gaussian distribution in Caucasian populations (Cholerton et al, 1992 Rautio et al, 1992), but some individuals are deficient in this activity. 

The hydroxylation of specific Pro residues in procollagen, the precursor of collagen, requires the action of the enzyme prolyl 4-hydroxylase. This enzyme (Mt 240,000) is an a2/32 tetramer in all vertebrate sources. The proline-hydroxylating activity is found in the a subunits. (Researchers were surprised to find that the )3 subunits are identical to the enzyme protein disulfide isomerase (PDI p. 152) these subunits do not participate in the prolyl hydroxylation activity.) Each a subunit contains one atom of nonheme iron (Fe2+), and the enzyme is one of a class of hydroxylases that require a-ketoglutarate in their reactions. 

In glucosides, hemiacetal hydroxyl activation/substitution can be achieved using a sulfonic anhydride and a nucleophile, plus a base as acid scavenger.12 The reaction is catalysed by dibutyl sulfoxide (Bu2S=0), and shows evidence of sulfur-covalent catalysis. Using benzenesulfonic anhydride [(PhS0)20], it is proposed to involve initial formation of a sulfonium sulfonate (6), the S(IV) centre of which then reacts with... 

Epoxidation and hydroxylation activity of iron(III) perfluorotetraphenylporphyrin biomimic was studied in a quartz flow reactor with the reaction zone 1.7 cm long and 1.8 cm in diameter. Kinetic regularities of monooxygenase reaction were studied at 180-320 °C and molar ratios C3H6 H202 equal 1 0.5 and 1 2. 

In the endosperm of immature Echinocystis fruits (50). From this latter material a cell-free system has been prepared which converted ABA to PA and DPA. The enzyme preparation was separated by centrifugation into a particulate fraction with ABA-hydroxylating activity and a soluble PA-reducing activity (50). 

Thummel KE, Shen DD, Carithers RL, et al. Prediction of in vivo midazolam clearance from hepatic CYP3A content and midazolam 1-hydroxylation activity in bver transplant patients. ISSX Proc 1993 4 235. 

Praeksaritanont T, Dwyer LM, Cribb AE. (+)-Bufuralol 1 -hydroxylation activity in human and rhesus monkey intestine and liver. Biochem Pharmacol 1995 50(9) 1521-1525. 

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