Produção Nacional
Pectinase production by Neurospora crassa: purification and biochemical characterization of extracellular polygalacturonase activity
1991; Microbiology Society; Volume: 137; Issue: 8 Linguagem: Inglês
10.1099/00221287-137-8-1815
ISSN2059-9323
AutoresMaria de Lourdes Teixeira de Moraes Polizeli, J. A. Jorge, Héctor F. Terenzi,
Tópico(s)Biofuel production and bioconversion
ResumoThe production of pectinase was studied in Neurospora crassa, using the hyperproducer mutant exo-1, which synthesized and secreted five to six times more enzyme than the wild-type. Polygalacturonase, pectin lyase and pectate lyase were induced by pectin, and this induction was glucose-repressible. Polygalacturonase was induced by galactose four times more efficiently than by pectin; in contrast the activity of lyases was not affected by galactose. The inducing effect of galactose on polygalacturonase was not glucose-repressible. Extracellular pectinases were separated by ion exchange chromatography. Pectate and pectin lyases eluted into three main fractions containing both activities; polygalacturonase eluted as a single, symmetrical peak, apparently free of other protein contaminants, and was purified 56-fold. The purified polygalacturonase was a monomeric glycoprotein (38% carbohydrate content) of apparent molecular mass 36·6–37.0 kDa (Sephadex G-100 and urea-SDS-PAGE, respectively). The enzyme hydrolysed predominantly polypectate. Pectin was also hydrolysed, but at 7% of the rate for polypectate. K m and V max for polypectate hydrolysis were 5·0 mg ml−1 and 357 μmol min−1 (mg protein)−1, respectively. Temperature and pH optima were 45°C and 6·0, respectively. The purified polygalacturonase reduced the viscosity of a sodium polypectate solution by 50%, with an increase of 7% in reducing sugar groups. The products of hydrolysis at initial reaction times consisted of oligogalacturonates without detectable monomer. Thus, the purified Neurospora crassa enzyme was classified as an endopolygalacturonase [poly(1,4-α-d-galacturonide) glycanohydrolase; EC 3.2.1.15].
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