Here we describe the first application of transient gene silencing in Saprolegnia parasitica, a pathogenic oomycete that infects a wide range of fish, amphibians, and crustaceans. A gene encoding a putative tyrosinase from S. parasitica, SpTyr, was selected to investigate the suitability of RNA-interference (RNAi) to functionally characterize genes of this economically important pathogen. Tyros...

Field bean (Dolichos lablab) contains a single isoform of PPO (polyphenol oxidase)--a type III copper protein that catalyses the o-hydroxylation of monophenols and oxidation of o-diphenols using molecular oxygen--and is a homotetramer with a molecular mass of 120 kDa. The enzyme is activated manyfold either in the presence of the anionic detergent SDS below its critical micellar concentration o...

BACKGROUND Tyrosinase is a bifunctional enzyme that catalyzes both the hydroxylation of monophenols to o-diphenols (monophenolase activity) and the subsequent oxidation of the diphenols to o-quinones (diphenolase activity). Due to the potential applications of tyrosinase in biotechnology, in particular in biocatalysis and for biosensors, it is desirable to develop a suitable low-cost process fo...

Claus T. Fuchs and Gerhard Spiteller Institut für Organische Chemie I, Universität Bayreuth, Universitätsstr. 30, D-95440 Bayreuth, Germany Z. Naturforsch. 53c, 799-805 (1998); received February 20/April 16, 1998 Taphrina pruni, Plums, Catechins, Caffeoyl-D-quinic Acids, Photometric Determination Plums (Prunus domestica) affected by the fungus Taphrina pruni and healthy ones were harvested in i...

Polyphenol oxidases (PPOs) have a recognized role during pathogen and arthropod attack. As an immediate consequence of such wounding, cellular compartmentation is destroyed allowing the chloroplastic PPO enzyme to interact with vacuolar substrates catalyzing the oxidation of monophenols and/or o-diphenols to o-diquinones. This ultimately results in a reduction in the nutritional value of wounde...

and comprises six species. One of these is Amberboa ramosa JAFRI, which is an annual herbaceous plant found in India and Pakistan. The plant has tonic, aperient, febrifuge, deobstruent, cytotoxic, and antibacterial activities. Previously triterpenoids, flavanoids, steroids, and steroidal glycosides have been reported from this species. Here we report the isolation and structure elucidation of l...

Tyrosinases, bifunctional metalloenzymes, catalyze the oxidation of monophenols and o-diphenols to o-quinones, the precursor compounds of the brown-coloured pigment melanin. In eukaryotic organisms, tyrosinases are expressed as latent zymogens that have to be proteolytically cleaved in order to form highly active enzymes. This activation mechanism, known as the tyrosinase maturation process, ha...

In fruits and vegetables, browning occurs due to the oxidation of polyphenols. Oxidative browning is catalysed by polyphenol oxidase (PPO; monophenol, dihydroxyphenyl alanine:oxygen oxidoreductase; EC.1.14.18.1). When fresh products are damaged oxidative browning occurs, and this is an economic problem for producers and consumers. Polyphenoloxidase, which is a copper-containing enzyme, catalyse...

Chlorogenic acid oxidase was extensively purified to homogeneity from apple flesh (Malus pumila cv. Fuji). The enzyme was purified 470-fold, with a total yield close to 70% from the plastid fraction by ammonium sulfate precipitation, gel filtration and ion-exchange chromatography. The molecular weight was determined to be 65,000 by both SDS-PAGE and gel filtration chromatography. The optimum pH...