RESUMO
The last step in the synthesis of lignin and suberin has been proposed to be catalyzed by peroxidases, although other proteins may also be involved. To determine which peroxidases are involved in the synthesis of lignin and suberin, five peroxidases from tomato (Lycopersicon esculentum) roots, representing the majority of the peroxidase activity in this organ, have been partially purified and characterized kinetically. The purified peroxidases with isoelectric point (pI) values of 3.6 and 9.6 showed the highest catalytic efficiency when the substrate used was syringaldazine, an analog of lignin monomer. Using a combination of transgenic expression and antibody recognition, we now show that the peroxidase pI 9.6 is probably encoded by TPX1, a tomato peroxidase gene we have previously isolated. In situ RNA hybridization revealed that TPX1 expression is restricted to cells undergoing synthesis of lignin and suberin. Salt stress has been reported to induce the synthesis of lignin and/or suberin. This stress applied to tomato caused changes in the expression pattern of TPX1 and induced the TPX1 protein. We propose that the TPX1 product is involved in the synthesis of lignin and suberin.
Assuntos
Lignina/biossíntese , Lipídeos de Membrana/biossíntese , Peroxidases/metabolismo , Solanum lycopersicum/enzimologia , Cinética , Lipídeos , Peroxidases/genéticaRESUMO
INTRODUCTION: Between 1985 and 1995, 3,860 cerebrospinal fluid (CSF) samples from patients with mycotic meningitis were analyzed. METHODS: Direct examination, cultures, complement fixation (CF) and immunodiffusion (ID) with Histoplasma capsulatum were carried out. RESULTS: Seventy four samples from 31 patients (three of them with AIDS) were reactive at the immunological assays. Cultures were positive in five patients. In 26 patients the clinical diagnosis together with positive CSF assays gave indirect evidence of meningeal histoplasmosis. ID and CF reactivity were 93.5% and 100% respectively. For 23 patients who had simultaneous examination of blood and CSF the double positivity was 78.2%. CONCLUSIONS: Because of the direct isolation of Histoplasma capsulatum is a difficult one, the diagnosis of subacute or chronic meningeal histoplasmosis may be confirmed by indirect immunological assays.