Ornithine decarboxylase in Paracoccidioides brasiliensis
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© Springer-Verlag 1996
O R I G I N A L PA P E R
Gioconda San-Blas · Françoise Sorais · Felipe San-Blas · José Ruiz-Herrera
Ornithine decarboxylase in Paracoccidioides brasiliensis
Received: 18 December 1995 / Accepted: 8 March 1996
Abstract Ornithine decarboxylase in Paracoccidioides brasiliensis, a dimorphic human pathogenic fungus, was more active at 37° C in the yeast phase and at 30° C in the mycelial phase. In contrast to other fungal systems, yeast growth and mycelium-to-yeast transition in P. brasiliensis were accompanied by a high activity of ornithine decarboxylase at the onset of the budding process, the activity of which was inhibited by 1,4-diamino-2-butanone. The activity of ornithine decarboxylase remained at a basal level during vegetative growth of both the mycelial phase and the late stage of yeast phase, and also through the yeast-to-mycelium transition. Key words Paracoccidioides brasiliensis · Fungal dimorphism · Ornithine decarboxylase Abbreviations DAB 1,4-Diamino-2-butanone · ODC Ornithine decarboxylase · M Mycelia · Y Yeasts
Introduction Polyamines are micromolecules necessary for cellular growth and differentiation. They originate from the decarboxylation of ornithine, which gives rise to putrescine, the first polyamine in the metabolic pathway. This reaction is catalyzed by ornithine decarboxylase (ODC; EC 4.1.1.17), one of the most highly regulated enzymes in eukaryotic systems (Tabor and Tabor 1984). ODC has been studied in
G. San-Blas · F. Sorais · F. San-Blas Instituto Venezolano de Investigaciones Científicas (IVIC), Centro de Microbiología y Biología Celular, Apartado 21827, Caracas 1020A, Venezuela Fax: +58-2-501-1382/572-7446 e-mail: [email protected]/[email protected] J. Ruiz-Herrera Centro de Investigación y de Estudios Avanzados (CINVESTAV) del IPN, Departamento de Ingeniería Genética, Unidad Irapuato, Irapuato, Gto, Mexico
several dimorphic fungi in which its activity correlates with morphogenetic processes. In Mucorales, ODC activity is lower in yeasts (Y) than in mycelia (M) (CalvoMéndez et al. 1987), increasing significantly during Y-toM transition and spore germination (Inderlied et al. 1980; Calvo-Méndez et al. 1987; Martínez-Pacheco et al. 1989; Ruiz-Herrera 1994). ODC is inhibited by 1,4-diamino-2butanone (DAB) (Stevens et al. 1977; Ruiz-Herrera and Calvo-Méndez 1987; Obregón et al. 1990; Ruiz-Herrera 1994), leading to changes in polyamine levels, which in turn are relevant to fungal dimorphism. It has been proposed that the effect of polyamines occurs through the inhibition of cytosine-DNA methylases, which may result in the regulation of gene expression at different developmental stages (Ruiz-Herrera et al. 1995). Paracoccidioides brasiliensis, another dimorphic fungus, is pathogenic for humans. Its geographical habitat is restricted to Latin America, where it produces one of the most frequent systemic mycoses in the region. Its dimorphic ability is related to virulence because the M phase, which grows at 20–23° C, must transform to a Y-like phase at 37°
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