Understanding Enzyme Inhibition

Ochs, Raymond S.

doi:10.1021/ed077p1453

Cited by 31 publications

(28 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It should be underlined that the mode of inhibition exerted by a compound has to be taken into account for understanding such an in-vivo effect. A competitive inhibition causes a substantial drop in enzyme activity at low substrate concentrations [83]. Thus, substrate accumulating over time will overcome the inhibition by two synergistically operating effects; the decreased inhibition seen at elevated substrate concentrations and the super-induction of the enzyme due to accumulating substrate, as was described [84].…”

Section: Induction Of Cell Stress Response By Cbsmentioning

confidence: 95%

Cannabidiol Protects Dopaminergic Neurons in Mesencephalic Cultures against the Complex I Inhibitor Rotenone Via Modulation of Heme Oxygenase Activity and Bilirubin

et al. 2020

View full text Add to dashboard Cite

Phytocannabinoids protect neurons against stressful conditions, possibly via the heme oxygenase (HO) system. In cultures of primary mesencephalic neurons and neuroblastoma cells, we determined the capability of cannabidiol (CBD) and tetrahydrocannabinol (THC) to counteract effects elicited by complex I-inhibitor rotenone by analyzing neuron viability, morphology, gene expression of IL6, CHOP, XBP1, HO-1 (stress response), and HO-2, and in vitro HO activity. Incubation with rotenone led to a moderate stress response but massive degeneration of dopaminergic neurons (DN) in primary mesencephalic cultures. Both phytocannabinoids inhibited in-vitro HO activity, with CBD being more potent. Inhibition of the enzyme reaction was not restricted to neuronal cells and occurred in a non-competitive manner. Although CBD itself decreased viability of the DNs (from 100 to 78%), in combination with rotenone, it moderately increased survival from 28.6 to 42.4%. When the heme degradation product bilirubin (BR) was added together with CBD, rotenone-mediated degeneration of DN was completely abolished, resulting in approximately the number of DN determined with CBD alone (77.5%). Using N18TG2 neuroblastoma cells, we explored the neuroprotective mechanism underlying the combined action of CBD and BR. CBD triggered the expression of HO-1 and other cell stress markers. Co-treatment with rotenone resulted in the super-induction of HO-1 and an increased in-vitro HO-activity. Co-application of BR completely mitigated the rotenone-induced stress response. Our findings indicate that CBD induces HO-1 and increases the cellular capacity to convert heme when stressful conditions are met. Our data further suggest that CBD via HO may confer full protection against (oxidative) stress when endogenous levels of BR are sufficiently high.

show abstract

Section: Induction Of Cell Stress Response By Cbsmentioning

confidence: 95%

Cannabidiol Protects Dopaminergic Neurons in Mesencephalic Cultures against the Complex I Inhibitor Rotenone Via Modulation of Heme Oxygenase Activity and Bilirubin

et al. 2020

View full text Add to dashboard Cite

show abstract

“…In cell-free assays, the extract dose-dependently inhibited the 5-LOX-mediated oxidation of linoleic acid, by reducing the maximal reaction velocity and the affinity of 5-LOX to its substrate. These findings collectively suggest that the effects of the extract on 5-LOX resembled a mixture of competitive and non-competitive enzyme inhibition [35]. Using a cell-based model of human inflammation, the cerumen extract additionally suppressed LTB 4 production by ionomycin-stimulated neutrophils.…”

Section: Discussionmentioning

confidence: 94%

Natural products isolated from Tetragonula carbonaria cerumen modulate free radical-scavenging and 5-lipoxygenase activities in vitro

Hamilton

Brooks

Ogbourne

et al. 2017

BMC Complement Altern Med

View full text Add to dashboard Cite

BackgroundPropolis and cerumen are plant-derived products found in honeybees and stingless bees, respectively. Although propolis is an ancient folk medicine, the bioactivities of cerumen obtained from Australian native stingless bees (Tetragonula carbonaria) have not been widely studied. Therefore, we investigated selected anti-oxidant and anti-inflammatory properties of T. carbonaria cerumen.MethodsA methanolic extract was prepared from the combined cerumen of 40 T. carbonaria hives, and HPLC was used to screen for chemical constituents that scavenged 2,2-azobis(2-methylpropionamidine) dihydrochloride (AAPH). The ability of cerumen extracts to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) and to interfere with leukotriene B4 (LTB4) production in ionomycin-stimulated human neutrophils was also examined.ResultsThe extract dose-dependently scavenged DPPH (EC50 = 27.0 ± 2.3 μg/mL); and inhibited the 5-lipoxygenase (5-LOX)-mediated oxidation of linoleic acid (IC50 = 67.1 ± 9.6 μg/mL). Pre-treatment of isolated human neutrophils with the methanolic cerumen extract additionally inhibited the ionomycin-stimulated production of LTB4 from these cells (IC50 = 13.3 ± 5.3 μg/mL). Following multi-solvent extraction, the free radical-scavenging and 5-LOX-inhibiting activities of the initial cerumen extract were retained in a polar, methanol-water extract, which contained gallic acid and a range of flavonone and phenolic natural products.ConclusionsThe findings identify free radical scavenging activity, and interference by extracts of T. carbonaria cerumen in 5-LOX–LTB4 signaling. Further investigation is needed to determine whether the extracts will provide therapeutic benefits for medical conditions in which oxidative stress and inflammation are implicated, including cardiovascular disease and impaired wound healing.

show abstract

“…O estudo cinético da reação pode ser efetuado pelo monitoramento da concentração do produto formado ou do substrato consumido, permitindo estimar a velocidade máxima da reação, a eficiência biocatalítica e a afinidade da enzima pelo substrato. Maiores detalhes de aspectos cinéticos de reações enzimáticas foram didaticamente descritos [7][8][9] . E + S ES E + P (2)…”

Section: Reações Enzimáticasunclassified

Um experimento de análise em fluxo envolvendo reações enzimáticas e quimiluminescência

Leite¹,

Fatibello‐Filho²,

Rocha³

2004

Quím. Nova

View full text Add to dashboard Cite

Recebido em 7/3/03; aceito em 13/8/03A FLOW ANALYSIS EXPERIMENT INVOLVING ENZYMATIC REACTIONS AND CHEMILUMINESCENCE. An experiment is proposed to introduce some fundamentals of flow analysis, chemiluminescence and kinetic monitoring of enzymatic reactions in undergraduate courses. Chemiluminescence detection is performed with a simple spectrophotometer equipped with a lab-made spiral flow cell constructed from a polyethylene tube. The hydrogen peroxide produced by the glucose oxidation in the presence of glucose oxidase is continuously monitored by the reaction with luminol in alkaline media in a flow injection system. The exercise allows also the discussion of important analytical features and the comparison with different optical methods of analysis.Keywords: chemiluminescence; flow analysis; enzymatic reactions. INTRODUÇÃOO desenvolvimento da Química e os trabalhos de interface com áreas correlatas têm gerado grandes desafios para o ensino desta ciên-cia. Um deles é a necessidade de incluir uma quantidade cada vez maior de conceitos, técnicas e informações importantes, sem que haja aumento do tempo dedicado às diferentes disciplinas. Uma alternativa para este problema é a proposição de experimentos que associem diferentes informações, permitindo explorar melhor o tempo disponível e, ao mesmo tempo, reduzir gastos. Essa estratégia também permite demonstrar que a compartimentalização da Química em diferentes áreas é artificial 1 , visto que a interpretação dos fenômenos com que o aluno se depara no dia-a-dia requer uma abordagem diferente, que utilize os conceitos químicos de maneira unificada e associada para seu entendimento. Os diferentes conceitos e técnicas introduzidos nas disciplinas de Química Analítica, por exemplo, são indispensáveis para a obtenção de informações relacionadas às outras disciplinas.Neste contexto, é proposto um experimento para alunos de graduação em Química e áreas correlatas, que permite introduzir conceitos relacionados à análise em fluxo, quimiluminescência, reações enzimáticas e cinética química. A reação de oxidação da glicose na presença de glicose oxidase (GOD) foi estudada através do monitoramento da quimiluminescência da oxidação do luminol pelo peróxido de hidrogênio produzido. Uma cela em espiral construída com tubo de polietileno e adaptada a um espectrofotômetro simples permite efetuar medidas por quimiluminescência com equipamentos usuais em laboratórios de ensino. QUIMILUMINESCÊNCIALuminescência é um termo empregado para descrever a emissão de radiação quando uma molécula ou átomo no estado excitado decai para o seu estado fundamental 2 . Os vários tipos de luminescência são caracterizados em função da fonte de energia empregada para se obter o estado excitado. Na quimiluminescência, a energia de excitação é proporcionada por uma reação química, sendo a emissão de radiação observada geralmente nas regiões do visível ou infravermelho próximo 3,4 . Esse processo pode ser simplificadamente representado pela Equação 1, onde A e B representam os reagentes, AB* o intermediár...

show abstract

Understanding Enzyme Inhibition

Cited by 31 publications

References 7 publications

Cannabidiol Protects Dopaminergic Neurons in Mesencephalic Cultures against the Complex I Inhibitor Rotenone Via Modulation of Heme Oxygenase Activity and Bilirubin

Cannabidiol Protects Dopaminergic Neurons in Mesencephalic Cultures against the Complex I Inhibitor Rotenone Via Modulation of Heme Oxygenase Activity and Bilirubin

Natural products isolated from Tetragonula carbonaria cerumen modulate free radical-scavenging and 5-lipoxygenase activities in vitro

Um experimento de análise em fluxo envolvendo reações enzimáticas e quimiluminescência

Contact Info

Product

Resources

About