RESUMO
The endogenous gibberellins in immature seeds of Prunus persica were analyzed by gas chromatography-mass spectrometry. Eleven known gibberellins, GA(3), GA(9), GA(17), GA(19), GA(30), GA(44), GA(61), GA(63), GA(87), GA(95) and GA(97) were identified. Additionally, several hitherto unknown gibberellins were detected and their putative structures were verified by synthesis of the authentic gibberellins. These gibberellins were then assigned trivial numbers, e.g. 1alpha-hydroxy GA(20) (GA(118)), 1alpha-hydroxy GA(9) (GA(119)), 1,2-didehydro GA(9) (GA(120)), 1,2-didehydro GA(70) (GA(121)), 1,2-didehydro GA(69) (GA(122)) and 1,2-didehydro GA(77) (GA(126)). GA(118) and GA(119) were the first 1alpha-hydroxy gibberellins identified from higher plants. The above profile of 1,2-didehydro gibberellins suggests that 1,2-dehydrogenation might occur prior to 3beta-hydroxylation in biosynthesis of GA(3), GA(30) and GA(87) in immature seeds of P. persica.
Assuntos
Giberelinas/metabolismo , Rosales/embriologia , Sementes/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Giberelinas/química , Espectroscopia de Ressonância MagnéticaRESUMO
In this study, we investigated seed and auxin regulation of gibberellin (GA) biosynthesis in pea (Pisum sativum L.) pericarp tissue in situ, specifically the conversion of [14C]GA19 to [14C]GA20. [14C]GA19 metabolism was monitored in pericarp with seeds, deseeded pericarp, and deseeded pericarp treated with 4-chloroindole-3-acetic acid (4-CI-IAA). Pericarp with seeds and deseeded pericarp treated with 4-CI-IAA continued to convert [14C]GA19 to [14C]GA20 throughout the incubation period (2-24 h). However, seed removal resulted in minimal or no accumulation of [14C]GA20 in pericarp tissue. [14C]GA29 was also identified as a product of [14C]GA19 metabolism in pea pericarp. The ratio of [14C]GA29 to [14C]GA20 was significantly higher in deseeded pericarp (with or without exogenous 4-CI-IAA) than in pericarp with seeds. Therefore, conversion of [14C]GA20 to [14C]GA29 may also be seed regulated in pea fruit. These data support the hypothesis that the conversion of GA19 to GA20 in pea pericarp is seed regulated and that the auxin 4-CI-IAA can substitute for the seeds in the stimulation of pericarp growth and the conversion of GA19 to GA20.
Assuntos
Giberelinas/metabolismo , Ácidos Indolacéticos/farmacologia , Pisum sativum/metabolismo , Sementes/fisiologia , Radioisótopos de Carbono , Homeostase , Cinética , Pisum sativum/efeitos dos fármacos , Técnica de Diluição de RadioisótoposRESUMO
Both cis- and trans-3-aminocyclobutane-1-carboxylic acid have been synthesized as conformationally restricted analogs of GABA. The cis isomer displayed weak to moderate GABA-like activity with respect to (1) inhibition of GABA uptake in rat brain minislices, (2) inhibition of sodium-independent binding of GABA to rat brain membranes, (3) activity as a substrate for GABA aminotransferase. and (4) depression of the firing rate of cat spinal neurons in vivo. The trans isomer was less effective on all four assays. The results has been interpreted in terms of the conformational "pinning back" of the polar groups by the cyclobutane ring in the trans GABA analog so that unfavorable steric interactions would occur between one of the methylene groups and a region of steric hindrance at the active sites for particular GABA processes.
Assuntos
Ciclobutanos , Ácido gama-Aminobutírico/análogos & derivados , 4-Aminobutirato Transaminase/metabolismo , Absorção , Animais , Encéfalo/enzimologia , Encéfalo/metabolismo , Ciclobutanos/síntese química , Ciclobutanos/farmacologia , Técnicas In Vitro , Conformação Molecular , Ratos , Medula Espinal/efeitos dos fármacos , Estereoisomerismo , Ácido gama-Aminobutírico/síntese química , Ácido gama-Aminobutírico/metabolismo , Ácido gama-Aminobutírico/farmacologiaAssuntos
Aminoácidos/metabolismo , Ciclopropanos/metabolismo , 4-Aminobutirato Transaminase/metabolismo , Aminoácidos/síntese química , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Gatos , Ciclopropanos/síntese química , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Ratos , Medula Espinal/efeitos dos fármacos , Medula Espinal/fisiologia , Relação Estrutura-Atividade , Ácido gama-Aminobutírico/metabolismoAssuntos
Encéfalo/metabolismo , Glutamatos/metabolismo , Ácido Caínico/farmacologia , Neurotoxinas , Pirrolidinas/farmacologia , Animais , Ligação Competitiva , Transporte Biológico Ativo/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Membrana Celular/metabolismo , Técnicas In Vitro , Cinética , Ratos , Receptores de Droga/efeitos dos fármacos , Receptores de Droga/metabolismo , Relação Estrutura-AtividadeRESUMO
S(+)-2,4-Diaminobutyric acid is at least 20 times more potent than the R(-) stereoisomer as an inhibitor of the sodium-dependent uptake of 4-aminobutyric acid (GABA) in rat brain slices. Both isomers, however, are equipotent as inhibitors of sodium-independent binding of GABA to membranes from rat brain. The latter finding may be relevant to the reported neurotoxicity in rats of both isomers of 2,4-diaminobutyric acid after intracisternal injection.
Assuntos
Aminobutiratos/metabolismo , Aminobutiratos/farmacologia , Encéfalo/metabolismo , Ácido gama-Aminobutírico/metabolismo , Animais , Transporte Biológico , Encéfalo/efeitos dos fármacos , Técnicas In Vitro , Ratos , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
Gabaculine, a conformationally restricted analogue of GABA, is (i) a moderately potent inhibitor (IC(50) 69 muM) of the sodium-dependent uptake of GABA in rat brain slices, (ii) ineffective at 100 muM as an inhibitor of the sodium-independent binding of GABA to membranes from rat brain, (iii) a relatively weak inhibitor (IC(50) > 1 mM) of glutamate decarboxylase activity in tracts of rat brain, and (iv) a very potent inhibitor (IC(50) 3 muM) of the transamination of GABA catalyzed by extracts of rat brain mitochondria. Inhibition of transamination is time-dependent and follows pseudo-first order kinetics, which is consistent with gabaculine acting as a catalytic inhibitor at the active site.
