Phenol oxidase activity of a monogenean, Paramazocraes thrissocles

The phenol oxidase of a monogenean, Paramazocraes thrissocles, oxidizes phenolic amines more effectively than other phenols studied. Based on the substrate specificity, the probable substrate for eggshell formation has been suggested. The enzyme shows the pH optimum of 7–2. At 40°C it shows maximum activity. Proenzyme is activated by metal ions and detergents. Copper chelating compounds strongly inhibit the enzyme.

Studies on the enzyme phenol oxidase in a freshwater monogenetic trematode

Cytochemical localization of the enzyme phenol oxidase inNeomurraytrema tengrahas been studied. Results reveal that the enzyme reacts with substrates such as catechol, hydroquinone, pyrogallol, dopa, doparmine, epinephrine and tyramine, but not with tyrosine and protocatechuic acid. Thus it shows activity with a wide range of phenols, aminated, mono and diphenols and also with deaminated and decarboxylated, di- and polyphenols. The maximum activity of the enzyme occurs between 40°C and 50°C with a pH optimum of 6–6.

Characterization of phenol oxidase in a pseudophyllidean cestode Penetrocephalus ganapatii

The biochemical characteristics of phenol oxidase obtained from Penetrocephalus ganapatii have been investigated using manometric and electrophoretic techniques. Phenol oxidase was found to have maximum activity at pH 7·4, the Michaelis constant for dopamine was 189 μM and the enzyme was stable between 20 and 40°C. Potassium cyanide, sodium diethyldithiocarbamate and phenylthiourea strongly suppressed enzyme activity. The Ki values for potassium cyanide, diethyldithiocarbamate and phenylthiourea were 33μM, 700 μM and 938 μM respectively. The properties of soluble and insoluble enzymes to various phenolic substrates are discussed.

Expression and characterization of two tyrosinases from the trematode Schistosoma japonicum

Tyrosinase (TYR) was thought to play a critical role during trematode egg production. In this study, we analyzed two genes (SjTYR1 and SjTYR2), derived from Schistosoma japonicum genome databases, which encode proteins with significant homologies to mammalian TYR. They exhibited the typical TYR topology, including two copper-binding domains and a highly conserved cysteine-rich domain. Semi-quantitative reverse transcription polymerase chain reaction showed that two SjTYR genes were mainly expressed in the female adult worm. A complementary DNA coding the putative common copper center domain of each SjTYR was cloned and inserted into a pET-28a-c(+) prokaryotic expression vector. After purification, the recombinant proteins expressed in Escherichia coli were used to produce their specific antibodies. The native active SjTYRs enzyme appeared to function as a homodimer, the subunits of which were linked to each other via covalent disulfide bonds. Both female and male worms possessed monophenol oxidase and diphenol oxidase activities of TYR. The relative enzymatic activities were 0.165 min(-1) mg(-1) and 0.0805 min(-1) mg(-1), which were inhibited by a copper-chelating agent (allyl thiourea) and correlated with disruption of female egg production. Our results revealed that SjTYRs might play a significant role during eggshell formation.

Electrophoretical and histochemical characterization of Schistosoma mansoni phenol oxidases

The phenol oxidase system, which is thought to play a central role in eggshell formation, was analyzed by means of electrophoretic and histochemical techniques. In contrast to current beliefs, our data show that males also express the phenol oxidase activity. The analysis of the electrophoretic pattern from males and females shows differences: adult males present a major band and a faint band, migrating slightly below. Adult females express a more complex pattern composed of four bands. Histochemical studies revealed that female phenol oxidase is concentrated in the vitelline cells, is inhibited by DDC, and this inhibition is correlated with disruption of female egg production. The present studies, in agreement with other reports, reveal that female phenol oxidase may be involved in sclerotization of the S. mansoni eggshell.

[Immunological aspects of the phenoloxidase enzymatic system of Schistosoma mansoni]

The phenol oxidase enzymatic system (EC 1.10.3.1, EC 1.10.3.2) is widespread in different species of the animal and vegetal kingdom. Despite its importance in the eggshell formation of the trematodes phenol oxidase (PO) has been little studied in these organisms, mainly in S. mansoni. This report presents the initial results concerning the immunization of rabbits with PO of S. mansoni and mushroom tyrosinase. The immunological analysis done by means of double immunodifusion (Ouchterlony) and immunoelectrophoresis techniques revealed some immunological identity between the PO of males and females. It was not seen cross reaction between the antisera against PO and tyrosinase, what suggests that the antigenic determinants of both enzymes are different in spite of their catalytic sites being similar, since they act over the same substrate. The results reported here represent a first step in way to obtain the PO isoenzymes in their pure form and should open new insights for further studies on the molecular mechanisms involved in the sclerotization process of the S. mansoni eggshell.

Properties of phenol oxidase in Fasciola gigantica

Phenol oxidase of Fasciola gigantica exists both as the soluble form as well as the membrane-bound form. The membrane-bound enzyme is considered to be a tyrosinase type because it is capable of oxidizing mono- and diphenol and is inefficient in oxidizing paraphenols. The soluble enzyme is a laccase type showing more affinity to various diphenols and paraphenols. Membrane-bound enzyme exists as isoenzymes, showing 3 fractions, of which the slow-moving fraction is capable of oxidizing both 4-methyl catechol and catechol, whereas the two remaining fractions are specific to 4-methyl catechol only. Soluble enzyme exists as a single homogeneous form showing affinity to both mono- and diphenols. Inhibition of the enzyme by potassium iodide and mercuric chloride indicates the active tyrosyl and SH groups of the enzyme. Inhibition of the enzyme by sodium diethyl dithiocarbamate and phenyl thiourea indicates that copper is the prosthetic group of the enzyme.

Activation of prophenol oxidase in the liver fluke Fasciola gigantica Cobbold

Activation of prophenol oxidase of Fasciola gigantica has been demonstrated using biochemical and electrophoretic techniques. Based on the difference in the electrophoretic pattern of the proenzyme and activated enzyme, a probable mechanism of activation of the prophenol oxidase is suggested. A role for Mehlis' gland in the activation process is suggested. The significance of the results is discussed in the light of related studies in insects.