RESUMO
Injection of 3,5,3' L-triiodothyronine (15 micrograms/100 g) induces a biphasic enhancement of rat heart ornithine decarboxylase (EC. 4.1.17) activity after 4 and 21 hours. This induction is observed after each daily injection, but to a lesser extent. The properties of partially purified basal enzyme and induced enzyme, at 21h, after single injections have been compared. 1) Affinity for ornithine is the same for both enzymes, but affinity for pyridoxal-phosphate is 40-fold higher for the induced one. 2) Thermostability studies suggest that basal and induced enzymes have different conformations. 3) The two enzymes have similar immuno-reactivity. 4) The comparisons of the time-dependent activity curve after injection and of the antigen/activity ratio suggests that triiodothyronine induces the synthesis of new molecules of enzymes and that an inhibition of the enzyme activity also occurs which explains the biphasic induction.
Assuntos
Carboxiliases/biossíntese , Miocárdio/enzimologia , Ornitina Descarboxilase/biossíntese , Tri-Iodotironina/farmacologia , Animais , Indução Enzimática , Coração/efeitos dos fármacos , Temperatura Alta , Masculino , Ornitina/metabolismo , Fosfato de Piridoxal/metabolismo , Ratos , Ratos EndogâmicosAssuntos
Cardiomegalia/metabolismo , AMP Cíclico/metabolismo , Proteínas Quinases/metabolismo , Tri-Iodotironina/farmacologia , Animais , Cardiomegalia/induzido quimicamente , GMP Cíclico/metabolismo , Citosol/enzimologia , Isoenzimas/metabolismo , Masculino , Miocárdio/ultraestrutura , Tamanho do Órgão/efeitos dos fármacos , RatosRESUMO
The expression of a previously cloned Dictyostelium discoideum spore-specific gene (Julien et al., EMBO J. 1, 1089-1093 (1982)) was investigated in wild type and mutant strains. In vitro translation of this spore-specific mRNA gave a protein of a molecular weight consistent with the mRNA size. Expressed at a low level during vegetative growth development and in stalk cells, the accumulation of this mRNA reached high values only in spore cells.