RESUMO
The 2.9-kb mRNA of 17 beta-hydroxysteroid dehydrogenase IV codes for an 80-kDa (737 amino acids) protein featuring domains that are not present in the other human 17 beta-hydroxysteroid dehydrogenases. The N-terminal part reveals conserved motifs of the short-chain alcohol dehydrogenase family. The central- and C-terminal domains are similar to peroxisomal enzymes for beta-oxidation of fatty acids and to sterol carrier protein 2. The 80-kDa protein is N-terminally cleaved to a 32-kDa fragment (amino acids 1-323). Both the 80-kDa and the N-terminal 32-kDa peptides are able to catalyze the dehydrogenation with steroids at the C17 position and with 3-hydroxyacyl-CoA. The central part of the 80-kDa protein (amino acids 324-596) catalyzes the 2-enoyl-acyl-CoA hydratase reaction with high efficiency. The C-terminal part of the 80-kDa protein (amino acids 597-737) facilitates the transfer of 7-dehydrocholesterol and phosphaidylcholine between membranes in vitro. The unique multidomain structure of the 80-kDa protein permits the catalysis of several reactions previously thought to be performed by complexes of different enzymes.
Assuntos
17-Hidroxiesteroide Desidrogenases/genética , 17-Hidroxiesteroide Desidrogenases/metabolismo , Acil Coenzima A/metabolismo , Enoil-CoA Hidratase , Complexos Multienzimáticos , Esteroides/metabolismo , Esteróis/metabolismo , 17-Hidroxiesteroide Desidrogenases/química , Animais , Clonagem Molecular , Feminino , Humanos , Hidroliases/metabolismo , Masculino , Proteína Multifuncional do Peroxissomo-2 , Placenta/enzimologia , Gravidez , Homologia de Sequência de Aminoácidos , Frações Subcelulares , Especificidade por Substrato , Testículo/enzimologiaRESUMO
17 beta-Hydroxysteroid dehydrogenase (17 beta-HSD) IV is coded by 2.9 kb mRNA translated to an 80 kDa protein which is N-terminally cleaved to a 32 kDa enzyme. The 17 beta-HSD IV is dedicated to steroid inactivation and reveals only 25% amino acid similarity with 17 beta-HSD I-III enzymes. Despite five Asn-Xaa-Ser/Thr (Xaa = unspecified amino acid) sites in the 80 kDa protein the enzyme is not glycosylated. The porcine 32 kDa 17 beta-HSD IV forms dimers of 75 kDa. The highest 17 beta-HSD IV mRNA expression and specific activities are found in liver and kidney followed by ovary and testes. In porcine gonads the immunofluorescence assigned the 17 beta-HSD IV to granulosa cells and to Leydig and Sertoli cells. As shown by the treatment with phorbol-myristate-acetate in vitamin D-differentiated monocytic leukemia THP1 cells, steroid synthesis and inactivation are regulated differentially by the protein kinase C pathway: an increase in aromatase is accompanied by a decrease in 17 beta-HSD IV mRNA levels.
Assuntos
17-Hidroxiesteroide Desidrogenases/metabolismo , 17-Hidroxiesteroide Desidrogenases/genética , 17-Hidroxiesteroide Desidrogenases/isolamento & purificação , Sequência de Aminoácidos , Animais , Northern Blotting , Linhagem Celular , Dimerização , Estradiol Desidrogenases/metabolismo , Feminino , Glicosilação , Humanos , Rim/embriologia , Rim/enzimologia , Masculino , Camundongos , Dados de Sequência Molecular , Ovário/enzimologia , Suínos , Testículo/enzimologiaRESUMO
Four types of 17beta-hydroxysteroid dehydrogenases have been identified so far. The porcine peroxisomal 17beta-hydroxysteroid dehydrogenase type IV catalyzes the oxidation of estradiol with high preference over the reduction of estrone. A 2.9-kilobase mRNA codes for an 80-kDa (737 amino acids) protein featuring domains which are not present in the other 17beta-hydroxysteroid dehydrogenases. The 80-kDa protein is N terminally cleaved to a 32-kDa fragment with 17beta-hydroxysteroid dehydrogenase activity. Here we show for the first time that both the 80-kDa and the N-terminal 32 kDa (amino acids 1-323) peptides are able to perform the dehydrogenase reaction not only with steroids at the C17 position but also with 3-hydroxyacyl-CoA. The central part of the 80-kDa protein (amino acids 324-596) catalyzes the 2-enoyl-acyl-CoA hydratase reaction with high efficiency. The C-terminal part of the 80-kDa protein (amino acids 597-737) is similar to sterol carrier protein 2 and facilitates the transfer of 7-dehydrocholesterol and phosphatidylcholine between membranes in vitro. The unique multidomain structure of the 80-kDa protein allows for the catalysis of several reactions so far thought to be performed by complexes of different enzymes.
