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Titolo:
NONSALT-LOSING MALE PSEUDOHERMAPHRODITISM DUE TO THE NOVEL HOMOZYGOUSN100S MUTATION IN THE TYPE-II 3-BETA-HYDROXYSTEROID DEHYDROGENASE GENE
Autore:
MEBARKI F; SANCHEZ R; RHEAUME E; LAFLAMME N; SIMARD J; FOREST MG; BEYOMAR F; DAVID M; LABRIE F; MOREL Y;
Indirizzi:
HOP DEBROUSSE,BIOCHIM ENDOCRINIENNE & MOLEC LAB,INSERM,U329,29 RUE SOEUR BOUVIER F-69322 LYON 05 FRANCE HOP DEBROUSSE,BIOCHIM ENDOCRINIENNE & MOLEC LAB,INSERM,U329 F-69322 LYON 05 FRANCE UNIV LYON,DEPT PEDIAT F-69322 LYON 05 FRANCE CHU LAVAL,RES CTR,MRC,MOLEC ENDOCRINOL GRP QUEBEC CITY PQ G1V 4G2 CANADA UNIV LAVAL QUEBEC CITY PQ G1V 4G2 CANADA
Titolo Testata:
The Journal of clinical endocrinology and metabolism
fascicolo: 7, volume: 80, anno: 1995,
pagine: 2127 - 2134
SICI:
0021-972X(1995)80:7<2127:NMPDTT>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
CONGENITAL ADRENAL-HYPERPLASIA; TISSUE-SPECIFIC EXPRESSION; DELTA-5-DELTA-4 ISOMERASE; 21-HYDROXYLASE DEFICIENCY; PERIPHERAL-TISSUES; VACCINIA VIRUS; 3-BETA-HSD; LIVER; AGE; TESTOSTERONE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
57
Recensione:
Indirizzi per estratti:
Citazione:
F. Mebarki et al., "NONSALT-LOSING MALE PSEUDOHERMAPHRODITISM DUE TO THE NOVEL HOMOZYGOUSN100S MUTATION IN THE TYPE-II 3-BETA-HYDROXYSTEROID DEHYDROGENASE GENE", The Journal of clinical endocrinology and metabolism, 80(7), 1995, pp. 2127-2134

Abstract

Recently, the structure of two genes encoding isoenzymes responsible for 3 beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4)-isomerase (3beta HSD) activity in the human was elucidated. This activity is an essential step in the biosynthesis of all classes of steroid hormones. In the classic severe form of 3 beta HSD deficiency, patients present with adrenal insufficiency, various degrees of salt loss, and incomplete masculinization in males. Here we report the characterization of the molecular basis of congenital adrenal hyperplasia due to 3 beta HSD deficiency in a male pseudohermaphrodite born from consanguineous parents and having no clinical, salt loss. To analyze the structure of thetype I and II 3 beta HSD genes of the patient, DNA fragments, generated by polymerase chain reaction amplification of the four exons and the exon-intron boundaries of these genes, were directly sequenced. The patient carried a homozygous missense mutation converting Asn(100) to Ser in exon 3 of his type II 3 beta HSD gene. His parents were heterozygous for the same point mutation. The absence of clinical salt loss associated with a male pseudohermaphroditism suggested that 3 beta HSD activity was impaired to different levels in the testes and adrenal. To elucidate whether this N100S missense mutation affected preferentially a steroidogenic pathway, enzymatic activity was analyzed by in vitro analysis of mutant recombinant enzyme generated by site-directed mutagenesis after its transient expression in COS-1 cells. Using homogenates from transferred cells:, the N100S 3 beta HSD enzyme showed a K-m value for pregnenolone of 25 +/- 3 mu mol/L compared with 3.5 +/- 0.2 mu mol/L for the normal human type II 3 beta HSD enzyme. Similar results were obtained using dehydroepiandrosterone as substrate. In addition to decreasing apparent affinity, the N100S mutation decreased the relative specific activity (V-max), leading to a relative specificity (relative V-max/K-m) 2.7% and 11% that of normal type II 3 beta HSD using pregnenolone or dehydroepiandrosterone as substrate, respectively. Moreover, the mutant N100S protein had an apparent decreased affinity for NAD(+), with a K-m value of 650 +/- 66 mu mol/L, compared with 20 +/- 2 mu mol/L for normal type II 3 beta HSD. Except for the hypothetical effect of local factors. these Findings suggest that a very weak residual activity DE the normal type II 3 beta HSD enzyme could prevent salt loss. but it was insufficient for normal male sex differentiationN100S is the first mutation to significantly affect both the affinityand specific activity of the type II 3 beta HSD enzyme for steroid substrates and for its cofactor, thus providing unique information aboutthe structure-activity relationships of the 3 beta HSD family. Conservation of Asn(100) in ail 3 beta HSD enzymes characterized so Far in mammalian as well as bacterial and viral members of the 3 beta HSD superfamily supports the crucial importance of this amino acid in the function of the enzyme.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 02/12/20 alle ore 14:21:27