title: A low-temperature polygalacturonase from P. occitanis: characterization and application in juice clarification.
abstract: An extracellular endo-polygalacturonase (PGase) was purified, after a single purification step, from the constitutive and hyperpectinolytic CT1 mutant of Penicillium occitanis. This enzyme named PG2 has a molecular weight of 42kDa. It was optimally active at 35°C and pH6 with more than 85% of activity at pH7 in contrast to the majority of fungal PGase, generally acting at 50°C and pH5. The specific activity obtained was among the highest ones, 31397.26U/mg. The PGase activity increased with the decrease of the degree of methylation (DM) of pectin, but it was also able to degrade the highly methyl-esterified substrates, 70% (DM) and 90% (DM), with almost 80% and 40% of residual activity respectively. Interestingly, PG2 is completely inhibited by DEPC, suggesting the implication of a Histidine residue in the active site. The sequencing of P. occitanis whole genome allowed us to identify the pga2 gene encoding PG2 and to localize the His residue, target of DEPC, while it was absent in the PG1 that resisted to DEPC. Besides that, the potentialities of PG2 have been put in use in juice clarification of pear, banana and citrus juice.
authors.affiliation: Laboratoire de Biotechnologie Moléculaire des Eucaryotes, Centre de Biotechnologie de Sfax, University of Sfax, BP1177, 3018 Sfax, Tunisia.
authors.forename: Azza Hadj
authors.initials: AH
authors.lastname: Sassi
authors.affiliation: Laboratoire de Biotechnologie Moléculaire des Eucaryotes, Centre de Biotechnologie de Sfax, University of Sfax, BP1177, 3018 Sfax, Tunisia.
authors.forename: Hajer
authors.initials: H
authors.lastname: Tounsi
authors.affiliation: Laboratoire de Biotechnologie Moléculaire des Eucaryotes, Centre de Biotechnologie de Sfax, University of Sfax, BP1177, 3018 Sfax, Tunisia.
authors.forename: Hèla
authors.initials: H
authors.lastname: Trigui-Lahiani
authors.affiliation: Laboratoire de Biotechnologie Moléculaire des Eucaryotes, Centre de Biotechnologie de Sfax, University of Sfax, BP1177, 3018 Sfax, Tunisia.
authors.forename: Rihab
authors.initials: R
authors.lastname: Bouzouita
authors.affiliation: Laboratoire de Biotechnologie Moléculaire des Eucaryotes, Centre de Biotechnologie de Sfax, University of Sfax, BP1177, 3018 Sfax, Tunisia.
authors.forename: Zamen Ben
authors.initials: ZB
authors.lastname: Romdhane
authors.affiliation: Laboratoire de Biotechnologie Moléculaire des Eucaryotes, Centre de Biotechnologie de Sfax, University of Sfax, BP1177, 3018 Sfax, Tunisia. Electronic address: Faouzi.gargouri@cbs.rnrt.tn.
authors.forename: Ali
authors.initials: A
authors.lastname: Gargouri
mesh_terms: D000595:Amino Acid Sequence; D004795:Enzyme Stability; D005511:Food Handling; D000067030:Fruit and Vegetable Juices; D006863:Hydrogen-Ion Concentration; D007460:Iodoacetamide / Q000378:metabolism; D008670:Metals / Q000494:pharmacology; D009154:Mutation; D010407:Penicillium / Q000201:enzymology* / Q000235:genetics; D011096:Polygalacturonase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D008670:Metals; D011096:Polygalacturonase; D007460:Iodoacetamide
keywords: Clarification; DEPC; Endo-PGase