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1.
Hered Cancer Clin Pract ; 19(1): 24, 2021 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-33836815

RESUMO

BACKGROUND: This nationwide study assessed the impact of nationally agreed cancer genetics guidelines on use of BRCA1/2 germline testing, risk management advice given by health professionals to women with pathogenic BRCA1/2 variants and uptake of such advice by patients. METHODS: Clinic files of 883 women who had initial proband screens for BRCA1/2 pathogenic variants at 12 familial cancer clinics between July 2008-July 2009 (i.e. before guideline release), July 2010-July 2011 and July 2012-July 2013 (both after guideline release) were audited to determine reason given for genetic testing. Separately, the clinic files of 599 female carriers without a personal history of breast/ovarian cancer who underwent BRCA1/2 predictive genetic testing and received their results pre- and post-guideline were audited to ascertain the risk management advice given by health professionals. Carriers included in this audit were invited to participate in a telephone interview to assess uptake of advice, and 329 agreed to participate. RESULTS: There were no significant changes in the percentages of tested patients meeting at least one published indication for genetic testing - 79, 77 and 78% of files met criteria before guideline, and two-, and four-years post-guideline, respectively (χ = 0.25, p = 0.88). Rates of documentation of post-test risk management advice as per guidelines increased significantly from pre- to post-guideline for 6/9 risk management strategies. The strategies with the highest compliance amongst carriers or awareness post-release of guidelines were annual magnetic resonance imaging plus mammography in women 30-50 years (97%) and annual mammography in women > 50 years (92%). Of women aged over 40 years, 41% had a risk-reducing bilateral mastectomy. Amongst women aged > 40 years, 75% had a risk-reducing salpingo-oophorectomy. Amongst women who had not had a risk-reducing bilateral mastectomy, only 6% took risk-reducing medication. Fear of side-effects was cited as the main reasons for not taking these medicines by 73% of women. CONCLUSIONS: Guidelines did not change the percentages of tested patients meeting genetic testing criteria but improved documentation of risk management advice by health professionals. Effective approaches to enhance compliance with guidelines are needed to improve risk management and quality of care.

2.
Artigo em Inglês | MEDLINE | ID: mdl-33660991

RESUMO

Au nanoparticles (NP) on TiO2 have been shown to be effective catalysts for selective oxidation reactions by using molecular oxygen. In this work, we have studied the influence of support morphology on the catalytic activity of Au/TiO2 catalysts. Two TiO2 anatase supports, a nanoplatelet-shaped material with predominantly the {001} facet exposed and a truncated bipyramidal-shaped nanoparticle with predominantly the {101} facet exposed, were prepared by using a nonaqueous solvothermal method and characterized by using DRIFTS, XPS, and TEM. Au nanoparticles were deposited on the supports by using the deposition-precipitation method, and particle sizes were determined by using STEM. Au nanoparticles were smaller on the support with the majority of the {101} facet exposed. The resulting materials were used to catalyze the aerobic oxidation of benzyl alcohol and trifluoromethylbenzyl alcohol. Support morphology impacts the catalytic activity of Au/TiO2; reaction rates for reactions catalyzed by the predominantly {101} material were higher. Much of the increased reactivity can be explained by the presence of smaller Au particles on the predominantly {101} material, providing more Au/TiO2 interface area, which is where catalysis occurs. The remaining modest differences between the two catalysts are likely due to geometric effects as Hammett slopes show no evidence for electronic differences between the Au particles on the different materials.

3.
J Inorg Biochem ; 219: 111409, 2021 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-33752122

RESUMO

Interest in understanding the environmental distribution of the alkane monooxygenase (AlkB) enzyme led to the identification of over 100 distinct alkane monooxygenase (AlkB) enzymes containing a covalently bound, or fused, rubredoxin. The rubredoxin-fused AlkB from Dietzia cinnamea was cloned as a full-length protein and as a truncated protein with the rubredoxin domain deleted. A point mutation (V91W) was introduced into the full-length protein, with the goal of assessing how steric bulk in the putative substrate channel might affect selectivity. Based on activity studies with alkane and alkene substrates, the rubredoxin-fused AlkB oxidizes a similar range of alkane substrates relative to its rubredoxin domain-deletion counterpart. Oxidation of terminal alkenes generated both an epoxide and a terminal aldehyde. The products of V91W-mutant-catalyzed oxidation of alkenes had a higher aldehyde-to-epoxide ratio than the products formed in the presence of the wild type protein. These results are consistent with this mutation causing a structural change impacting substrate positioning.

4.
Int J Cardiol ; 330: 128-134, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33581180

RESUMO

BACKGROUND: This sub-study of the Australian Genomics Cardiovascular Genetic Disorders Flagship sought to conduct the first nation-wide audit in Australia to establish the current practices across cardiac genetics clinics. METHOD: An audit of records of patients with a suspected genetic heart disease (cardiomyopathy, primary arrhythmia, autosomal dominant congenital heart disease) who had a cardiac genetics consultation between 1st January 2016 and 31 July 2018 and were offered a diagnostic genetic test. RESULTS: This audit included 536 records at multidisciplinary cardiac genetics clinics from 11 public tertiary hospitals across five Australian states. Most genetic consultations occurred in a clinic setting (90%), followed by inpatient (6%) and Telehealth (4%). Queensland had the highest proportion of Telehealth consultations (9% of state total). Sixty-six percent of patients had a clinical diagnosis of a cardiomyopathy, 28% a primary arrhythmia, and 0.7% congenital heart disease. The reason for diagnosis was most commonly as a result of investigations of symptoms (73%). Most patients were referred by a cardiologist (85%), followed by a general practitioner (9%) and most genetic tests were funded by the state Genetic Health Service (73%). Nationally, 29% of genetic tests identified a pathogenic or likely pathogenic gene variant; 32% of cardiomyopathies, 26% of primary arrhythmia syndromes, and 25% of congenital heart disease. CONCLUSION: We provide important information describing the current models of care for genetic heart diseases throughout Australia. These baseline data will inform the implementation and impact of whole genome sequencing in the Australian healthcare landscape.

5.
Eur J Neurosci ; 51(6): 1504-1513, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31502721

RESUMO

Zinc is important in neurogenesis, but excessive levels can cause apoptosis and other pathologies leading to cognitive impairments. Mast cells are present in many brain regions including the hippocampus, an area rich in vesicular zinc. Mast cells contain zinc-rich granules and a well-developed mechanism for uptake of zinc ions; both features point to the potential for a role in zinc homeostasis. Prior work using the Timm stain supported this hypothesis, as increased labile zinc was detected in the hippocampus of mast cell-deficient mice compared to wild-type mice while no differences in total zinc were found between the two genotypes in the whole brain or other tissues. The current report further examines differences in zinc homeostasis between wild-type and mast cell-deficient mice by exploring the zinc transporter ZnT3, which transports labile zinc into synaptic vesicles. The first study used immunocytochemistry to localize ZnT3 within the mossy fibre layer of the hippocampus to determine whether there was differential expression of ZnT3 in wild-type versus mast cell-deficient mice. The second study used inductively coupled plasma mass spectrometry (ICP-MS) to determine total zinc content in the whole dentate gyrus of the two genotypes. The immunocytochemical results indicate that there are higher levels of ZnT3 localized to the mossy fibre layer of the dentate gyrus of mast cell-deficient mice than in wild-type mice. The ICP-MS data reveal no differences in total zinc in dentate gyrus as a whole. The results are consistent with the hypothesis that mast cells participate in zinc homeostasis at the level of synaptic vesicles.

6.
Hum Mutat ; 40(9): 1557-1578, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31131967

RESUMO

The multifactorial likelihood analysis method has demonstrated utility for quantitative assessment of variant pathogenicity for multiple cancer syndrome genes. Independent data types currently incorporated in the model for assessing BRCA1 and BRCA2 variants include clinically calibrated prior probability of pathogenicity based on variant location and bioinformatic prediction of variant effect, co-segregation, family cancer history profile, co-occurrence with a pathogenic variant in the same gene, breast tumor pathology, and case-control information. Research and clinical data for multifactorial likelihood analysis were collated for 1,395 BRCA1/2 predominantly intronic and missense variants, enabling classification based on posterior probability of pathogenicity for 734 variants: 447 variants were classified as (likely) benign, and 94 as (likely) pathogenic; and 248 classifications were new or considerably altered relative to ClinVar submissions. Classifications were compared with information not yet included in the likelihood model, and evidence strengths aligned to those recommended for ACMG/AMP classification codes. Altered mRNA splicing or function relative to known nonpathogenic variant controls were moderately to strongly predictive of variant pathogenicity. Variant absence in population datasets provided supporting evidence for variant pathogenicity. These findings have direct relevance for BRCA1 and BRCA2 variant evaluation, and justify the need for gene-specific calibration of evidence types used for variant classification.


Assuntos
Proteína BRCA1/genética , Proteína BRCA2/genética , Biologia Computacional/métodos , Mutação de Sentido Incorreto , Neoplasias/diagnóstico , Processamento Alternativo , Detecção Precoce de Câncer , Feminino , Predisposição Genética para Doença , Humanos , Funções Verossimilhança , Masculino , Herança Multifatorial , Neoplasias/genética
7.
Metallomics ; 11(2): 349-361, 2019 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-30516222

RESUMO

The toxicity of lead, one of the most ubiquitous toxic metals, is well known. Some of its pathological effects are related to its preference for the sulfhydryl groups of proteins. Metallothioneins (MT) are a particular family of metalloproteins characterized by their high Cys content that, among other functions, are linked to the detoxification of heavy metals. In mammals, 4 MT isoforms have been found. The MT3 isoform, also called "neuronal growth inhibitory factor", is mainly synthesized in the brain and contains several structural differences that may contribute to important functional differences between it and other MT isoforms. The abilities of recombinant MT3 and its individual αMT3 and ßMT3 fragments to bind Pb(ii) have been investigated here, under different pH conditions, by means of spectroscopy, mass spectrometry and isothermal titration calorimetry. The results obtained show that the binding of Pb(ii) to the intact MT3 protein is relatively unaffected by pH, while the individual domains interact with Pb(ii) in a pH-sensitive manner. The mass spectrometry data reveal the evolution with time of the initially formed Pb-MT complexes. In the case of the full length protein, Pb(ii) remains bound for a long period of time. With the isolated fragments, the lead is eventually released. The Pb-species formed depend on the amount of Pb(ii) present in solution. The thermodynamic data recorded, as measured by ITC, for the replacement of Zn(ii) by Pb(ii) in reactions with Zn-MT3, Zn-αMT3 and Zn-ßMT3 are all similar, and in all cases, the displacement of Zn(ii) by Pb(ii) is thermodynamically favorable. Zn-Replete and Pb-replete MT3 have distinctive circular dichroism spectra, suggestive of structural differences with different metallation status.


Assuntos
Encéfalo/metabolismo , Chumbo/metabolismo , Metaloproteinase 16 da Matriz/metabolismo , Metalotioneína/metabolismo , Sequência de Aminoácidos , Animais , Humanos , Metaloproteinase 16 da Matriz/química , Metalotioneína/química , Camundongos , Dados de Sequência Molecular , Ligação Proteica , Zinco/metabolismo
8.
Cancer Cell ; 33(4): 620-633.e6, 2018 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-29634949

RESUMO

The canine transmissible venereal tumor (CTVT) is a clonally transmissible cancer that regresses spontaneously or after treatment with vincristine, but we know little about the regression mechanisms. We performed global transcriptional, methylation, and functional pathway analyses on serial biopsies of vincristine-treated CTVTs and found that regression occurs in sequential steps; activation of the innate immune system and host epithelial tissue remodeling followed by immune infiltration of the tumor, arrest in the cell cycle, and repair of tissue damage. We identified CCL5 as a possible driver of CTVT regression. Changes in gene expression are associated with methylation changes at specific intragenic sites. Our results underscore the critical role of host innate immunity in triggering cancer regression.


Assuntos
Doenças do Cão/tratamento farmacológico , Perfilação da Expressão Gênica/veterinária , Redes Reguladoras de Genes/efeitos dos fármacos , Tumores Venéreos Veterinários/tratamento farmacológico , Vincristina/administração & dosagem , Animais , Pontos de Checagem do Ciclo Celular , Quimiocina CCL5/genética , Metilação de DNA , Doenças do Cão/genética , Cães , Feminino , Regulação Neoplásica da Expressão Gênica , Imunidade Inata/efeitos dos fármacos , Masculino , Análise de Sequência de RNA/veterinária , Tumores Venéreos Veterinários/genética , Vincristina/farmacologia
9.
Biochemistry ; 56(26): 3347-3357, 2017 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-28603981

RESUMO

OleT is a cytochrome P450 enzyme that catalyzes the removal of carbon dioxide from variable chain length fatty acids to form 1-alkenes. In this work, we examine the binding and metabolic profile of OleT with shorter chain length (n ≤ 12) fatty acids that can form liquid transportation fuels. Transient kinetics and product analyses confirm that OleT capably activates hydrogen peroxide with shorter substrates to form the high-valent intermediate Compound I and largely performs C-C bond scission. However, the enzyme also produces fatty alcohol side products using the high-valent iron oxo chemistry commonly associated with insertion of oxygen into hydrocarbons. When presented with a short chain fatty acid that can initiate the formation of Compound I, OleT oxidizes the diagnostic probe molecules norcarane and methylcyclopropane in a manner that is reminiscent of reactions of many CYP hydroxylases with radical clock substrates. These data are consistent with a decarboxylation mechanism in which Compound I abstracts a substrate hydrogen atom in the initial step. Positioning of the incipient substrate radical is a crucial element in controlling the efficiency of activated OH rebound.


Assuntos
Proteínas de Bactérias/metabolismo , Caproatos/metabolismo , Caprilatos/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Ácidos Decanoicos/metabolismo , Ácidos Láuricos/metabolismo , Micrococcus/enzimologia , Modelos Moleculares , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Biocatálise , Biocombustíveis/análise , Caprilatos/química , Carboxiliases/química , Carboxiliases/genética , Carboxiliases/metabolismo , Domínio Catalítico , Ciclopropanos/química , Ciclopropanos/metabolismo , Sistema Enzimático do Citocromo P-450/química , Sistema Enzimático do Citocromo P-450/genética , Ácidos Decanoicos/química , Descarboxilação , Guaiacol/metabolismo , Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/metabolismo , Ácidos Láuricos/química , Conformação Molecular , Oxirredução , Especificidade por Substrato , Terpenos/química , Terpenos/metabolismo
10.
Int J Mol Sci ; 18(6)2017 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-28587098

RESUMO

A study of factors proposed to affect metallothionein-3 (MT3) function was carried out to elucidate the opaque role MT3 plays in human metalloneurochemistry. Gene expression of Mt2 and Mt3 was examined in tissues extracted from the dentate gyrus of mouse brains and in human neuronal cell cultures. The whole-genome gene expression analysis identified significant variations in the mRNA levels of genes associated with zinc homeostasis, including Mt2 and Mt3. Mt3 was found to be the most differentially expressed gene in the identified groups, pointing to the existence of a factor, not yet identified, that differentially controls Mt3 expression. To examine the expression of the human metallothioneins in neurons, mRNA levels of MT3 and MT2 were compared in BE(2)C and SH-SY5Y cell cultures treated with lead, zinc, cobalt, and lithium. MT2 was highly upregulated by Zn2+ in both cell cultures, while MT3 was not affected, and no other metal had an effect on either MT2 or MT3.


Assuntos
Metalotioneína/genética , Metalotioneína/metabolismo , Neurônios/metabolismo , Animais , Giro Denteado/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica/efeitos dos fármacos , Íons/metabolismo , Íons/farmacologia , Metais/metabolismo , Metais/farmacologia , Camundongos , Neurônios/efeitos dos fármacos , Proteostase/genética , Zinco/metabolismo
12.
Metallomics ; 8(6): 579-88, 2016 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-26745006

RESUMO

Childhood lead poisoning is a costly and largely preventable public health problem that lowers IQs, decreases attention spans, and leads to the development of other childhood intellectual disabilities. Furthermore, recent evidence links developmental lead poisoning with the etiology of disorders that appear much later in life, such as Alzheimer's disease, Parkinson's disease, and schizophrenia. Little is known about how lead influences the onset of these disorders. This paper reviews the evidence that lead substitution for zinc in zinc-finger proteins contributes to the development of Alzheimer's disease, Parkinson's disease, and schizophrenia. The zinc-finger proteins potentially impacted by lead include DNA methyltransferase 1 (DNMT1) and Presenilin 1 and 2 (PSEN1/2) in Alzheimer's disease, the dopamine receptor in Parkinson's disease, and the NMDA receptor, zinc-finger protein 804A (ZNF804A), and disrupted-in-schizophrenia 1 (DISC1)-binding zinc-finger (DBZ) in schizophrenia.


Assuntos
Chumbo/efeitos adversos , Transtornos Mentais/etiologia , Saúde Mental , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/metabolismo , Dedos de Zinco , Humanos , Transtornos Mentais/patologia
13.
Cell Syst ; 1(3): 210-223, 2015 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-26645048

RESUMO

Tumors are typically sequenced to depths of 75-100× (exome) or 30-50× (whole genome). We demonstrate that current sequencing paradigms are inadequate for tumors that are impure, aneuploid or clonally heterogeneous. To reassess optimal sequencing strategies, we performed ultra-deep (up to ~312×) whole genome sequencing (WGS) and exome capture (up to ~433×) of a primary acute myeloid leukemia, its subsequent relapse, and a matched normal skin sample. We tested multiple alignment and variant calling algorithms and validated ~200,000 putative SNVs by sequencing them to depths of ~1,000×. Additional targeted sequencing provided over 10,000× coverage and ddPCR assays provided up to ~250,000× sampling of selected sites. We evaluated the effects of different library generation approaches, depth of sequencing, and analysis strategies on the ability to effectively characterize a complex tumor. This dataset, representing the most comprehensively sequenced tumor described to date, will serve as an invaluable community resource (dbGaP accession id phs000159).

14.
Metallomics ; 6(6): 1105-6, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24830347

RESUMO

This editorial introduces the Metallomics themed issue Metals in Marine Biochemistry, guest edited by Rachel Austin and Mak Saito.


Assuntos
Biologia Marinha , Metais/análise , Metais/metabolismo , Animais , Organismos Aquáticos/química , Organismos Aquáticos/metabolismo , Bioquímica , Oceanos e Mares
15.
Metallomics ; 6(6): 1121-5, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24710692

RESUMO

Should iron and copper be added to the environment to stimulate the natural bioremediation of marine oil spills? The key enzymes that catalyze the oxidation of alkanes require either iron or copper, and the concentration of these ions in seawater is vanishingly low. Nevertheless, the dependence of alkane oxidation activity on external metal concentrations remains unclear. This perspective will summarize what is known about the co-regulation of alkane oxidation and metal acquisition and pose a series of critical questions to which, for the most part, we do not yet have answers. The paucity of answers points to the need for additional studies to illuminate the cellular biology connecting microbial growth on alkanes to the acquisition of metal ions.


Assuntos
Alcanos/metabolismo , Bactérias/metabolismo , Cobre/metabolismo , Ferro/metabolismo , Metais/metabolismo , Biodegradação Ambiental , Cobre/análise , Ferro/análise , Oxirredução , Água do Mar/análise
16.
Front Microbiol ; 4: 338, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24312086
17.
Front Microbiol ; 4: 109, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23825470

RESUMO

Six aerobic alkanotrophs (organism that can metabolize alkanes as their sole carbon source) isolated from deep-sea hydrothermal vents were characterized using the radical clock substrate norcarane to determine the metalloenzyme and reaction mechanism used to oxidize alkanes. The organisms studied were Alcanivorax sp. strains EPR7 and MAR14, Marinobacter sp. strain EPR21, Nocardioides sp. strains EPR26w, EPR28w, and Parvibaculum hydrocarbonoclasticum strain EPR92. Each organism was able to grow on n-alkanes as the sole carbon source and therefore must express genes encoding an alkane-oxidizing enzyme. Results from the oxidation of the radical-clock diagnostic substrate norcarane demonstrated that five of the six organisms (EPR7, MAR14, EPR21, EPR26w, and EPR28w) used an alkane hydroxylase functionally similar to AlkB to catalyze the oxidation of medium-chain alkanes, while the sixth organism (EPR92) used an alkane-oxidizing cytochrome P450 (CYP)-like protein to catalyze the oxidation. DNA sequencing indicated that EPR7 and EPR21 possess genes encoding AlkB proteins, while sequencing results from EPR92 confirmed the presence of a gene encoding CYP-like alkane hydroxylase, consistent with the results from the norcarane experiments.

18.
J Inorg Biochem ; 121: 46-52, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23337786

RESUMO

An alkane hydroxylase from the marine organism Alcanivorax borkumensis (AbAlkB) was purified. The purified protein retained high activity in an assay with purified rubredoxin (AlkG), purified maize ferredoxin reductase, NADPH, and selected substrates. The reaction mechanism of the purified protein was probed using the radical clock substrates bicyclo[4.1.0]heptane (norcarane), bicyclo[3.1.0]hexane (bicyclohexane), methylphenylcyclopropane and deuterated and non-deuterated cyclohexane. The distribution of products from the radical clock substrates supports the hypothesis that purified AbAlkB hydroxylates substrates by forming a substrate radical. Experiments with deuterated cyclohexane indicate that the rate-determining step has a significant CH bond breaking character. The products formed from a number of differently shaped and sized substrates were characterized to determine the active site constraints of this AlkB. AbAlkB can catalyze the hydroxylation of a large number of aromatic compounds and linear and cyclic alkanes. It does not catalyze the hydroxylation of alkanes with a chain length longer than 15 carbons, nor does it hydroxylate sterically hindered C-H bonds.


Assuntos
Alcanivoraceae/enzimologia , Proteínas de Bactérias/química , Citocromo P-450 CYP4A/química , Rubredoxinas/química , Alcanivoraceae/química , Proteínas de Bactérias/isolamento & purificação , Biodegradação Ambiental , Compostos Bicíclicos com Pontes/química , Cicloexanos/química , Ciclopropanos/química , Citocromo P-450 CYP4A/isolamento & purificação , Radicais Livres/química , Hidroxilação , Modelos Moleculares , NADP/química , Oxirredução , Proteínas de Plantas/química , Proteínas de Plantas/isolamento & purificação , Rubredoxinas/isolamento & purificação , Especificidade por Substrato , Terpenos/química , Zea mays/química , Zea mays/enzimologia
19.
J Am Chem Soc ; 134(50): 20365-75, 2012 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-23157204

RESUMO

A purified and highly active form of the non-heme diiron hydroxylase AlkB was investigated using the diagnostic probe substrate norcarane. The reaction afforded C2 (26%) and C3 (43%) hydroxylation and desaturation products (31%). Initial C-H cleavage at C2 led to 7% C2 hydroxylation and 19% 3-hydroxymethylcyclohexene, a rearrangement product characteristic of a radical rearrangement pathway. A deuterated substrate analogue, 3,3,4,4-norcarane-d(4), afforded drastically reduced amounts of C3 alcohol (8%) and desaturation products (5%), while the radical rearranged alcohol was now the major product (65%). This change in product ratios indicates a large kinetic hydrogen isotope effect of ∼20 for both the C-H hydroxylation at C3 and the desaturation pathway, with all of the desaturation originating via hydrogen abstraction at C3 and not C2. The data indicate that AlkB reacts with norcarane via initial C-H hydrogen abstraction from C2 or C3 and that the three pathways, C3 hydroxylation, C3 desaturation, and C2 hydroxylation/radical rearrangement, are parallel and competitive. Thus, the incipient radical at C3 either reacts with the iron-oxo center to form an alcohol or proceeds along the desaturation pathway via a second H-abstraction to afford both 2-norcarene and 3-norcarene. Subsequent reactions of these norcarenes lead to detectable amounts of hydroxylation products and toluene. By contrast, the 2-norcaranyl radical intermediate leads to C2 hydroxylation and the diagnostic radical rearrangement, but this radical apparently does not afford desaturation products. The results indicate that C-H hydroxylation and desaturation follow analogous stepwise reaction channels via carbon radicals that diverge at the product-forming step.


Assuntos
Ferro/metabolismo , Oxigenases de Função Mista/metabolismo , Hidroxilação , Espectrometria de Massas , Oxigenases de Função Mista/isolamento & purificação , Oxirredução , Especificidade por Substrato
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