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A Marchesini

Publications and source records attributed to A Marchesini.

36 records · Page 2Linked to original sources
PubMed1989

Putative mesothelial cell growth-promoting activity of a cytoplasmic protein expressed by the mesothelial cell. A preliminary report.

Mesothelioma cells produce a cytoplasmic protein unique to primary tumours of the mesothelium which induces the in vitro proliferation of human mesothelial cells in a dose-dependent fashion. When a polyclonal antibody to this protein was added to cultures of human mesothelioma cells, inhibition of their growth occurred. These results provide evidence for a growth-factor-like role of this mesothelial protein that may act through an autocrine mechanism.

Cell Division↗
PubMed1988

Azide-binding studies reveal type 3 copper heterogeneity in ascorbate oxidase from the green zucchini squash (Cucurbita pepo).

Titration of native ascorbate oxidase from green zucchini squash (Cucurbita pepo) with azide in 0.1 M-phosphate buffer, pH 6.8, exhibits a biphasic spectral behaviour. Binding of the anion with 'high affinity' (K greater than 5000 M-1) produces a broad increase of absorption in the 400-500 nm region (delta epsilon approximately 1000 M-1.cm-1) and c.d. activity in the 300-450 nm region, whereas azide binding with 'low affinity' (K approximately 100 M-1) is characterized by an intense absorption band at 420 nm (delta epsilon = 6000 M-1.cm-1), corresponding to negative c.d. activity and a decrease of absorption at 330 nm (delta epsilon = -2000 M-1.cm-1). The high-affinity binding involves a minor fraction of the protein containing Type 3 copper in the reduced state, and the spectral features of this azide adduct can be eliminated by treatment of the native enzyme with small amounts of H2O2, followed by dialysis before azide addition. As shown by e.s.r. spectroscopy, Type 2 copper is involved in both types of binding, its signal being converted into that of a species with small hyperfine splitting constant [12 mT (approximately 120 G)] in the case of the low-affinity azide adduct. The spectral similarities of the two types of azide adducts with the corresponding adducts formed by native laccase, which also exhibits Type 3 copper heterogeneity, are discussed.

Ascorbate Oxidase↗
PubMed1986

New marker for mesothelioma: an immunoperoxidase study.

An antibody was raised against a protein isolated from the cytoplasm of mesothelioma cells. It was subsequently used in an immunoperoxidase procedure on formalin fixed, paraffin embedded tissue sections. A representative sample of benign and malignant tumours from all the systems of the human body was examined. All the tumours derived from coelomic surfaces (mesotheliomas of pleura, peritoneum, and ovary, and adenomatoid tumour of epididymis) reacted with the antibody. No other tumour tested in this study expressed the protein. These findings indicate that the antibody may be useful in the identification of mesothelioma cells in both histological and cytological diagnostic routine practice when morphological interpretation is in doubt.

Antibodies, Neoplasm↗
PubMed1985

Isolation and characterization of a possible new protein marker for differential diagnosis between metastatic carcinoma and mesothelioma cells in serous effusions: preliminary findings.

A distinctive diagnostic staining pattern of the cytoplasm of reactive and neoplastic mesothelial cells in serous effusions was assumed to be caused by a specific compound. This was isolated by polyacrylamide gel electrophoresis and corresponded to a protein with an apparent molecular weight around 200,000. Isoelectric point was found to be 8.7. This protein contained high proportions of glutamic acid, serine, and glycine.

Ascitic Fluid↗
PubMed1983

A reinvestigation on the quaternary structure of ascorbate oxidase from Cucurbita pepo medullosa.

The optical properties, copper content, catalytic activity and quaternary structure of many preparations of ascorbate oxidase purified with two different methods were examined. Fresh samples appeared identical and were characterized by optical ratios A280/A610 = 25 +/- 1 and A330/A610 = 0.8 +/- 0.05, by specific activity toward ascorbate of 3.48 +/- 0.05 mol g-1 min-1 and by a copper content of 8 +/- 0.3 mol/145 000 Mr. The enzyme is composed of two non-covalently linked subunits of slightly different molecular mass (75 000 and 72 000 respectively). These subunits cannot be further resolved by reduction of disulfide bonds. Proteolytic cleavage of the protein chains was observed during purification and storage in the absence of the protease inhibitor 6-amino caproic acid. Ascorbate oxidase exists as a monomer at neutral pH and undergoes reversible association into higher molecular weight species at slightly acid pH values. Association is not accompanied by spectroscopic or catalytic changes.

Ascorbate Oxidase↗
PubMed1979

Ascorbate oxidase from Cucurbita pepo medullosa. New method of purification and reinvestigation of properties.

1. Ascorbate oxidase has been isolated from the green squash Cucurbita pepo medullosa by a new purification method. Furthermore a low-molecular-weight copper protein containing one type-1 copper/20000 Mr could be separated during the purification of the oxidase. The six-step procedure developed improved the yield of ascorbate oxidase by a factor of 2.5. The method is well reproducible and a constant value of 8 Cu (7.95 +/- 0.1/140000 Mr) has been established. By ultracentrifugal and electrophoretic criteria the enzyme preparations have been found to be homogeneous. They exhibited a specific activity of 3930 +/- 50 units/mg protein or 1088 +/- 15 units/microgram copper. 2. The pure enzyme is characterized by the following optical purity indices: A280/A610 = 25 +/- 0.5, A330/A610 = 0.65 +/- 0.05 and A610/A500 = 7.0 +/- 0.25. The molar absorption coeffient of the characteristic absorption maximum at 610 nm (oxidized minus reduced) amounts of 9700 M-1 cm-1 . 3. Computer simulations of the electron paramagnetic resonance (EPR) spectra of the oxidized enzyme reveal the following parameters: for the type-1 (blue) copper gz = 2.227, gy = 2.058, gx = 2.036; Az = 5.0 mT, Ay = Ax = 0.5 mT, for the type-2 (non-blue) copper g parallel to = 2.242, g perpendicular = 2.053; A parallel to = 19.0 mT, A perpendicular 0.5 mT. Out of the eight copper atoms present in the oxidase four are detectable by EPR. Of these, three belong to the type-1 class, and one to the type-2 class, as demonstrated by computer simulations of the EPR spectra. 4. To achieve full reduction of the enzyme, as measured by bleaching of the blue chromophore, four equivalents of L-ascorbate or reductase must be added in the absence of molecular oxygen. Upon reduction of the enzyme the fluorescence at 330 nm (lambda max ex = 295 nm) is enhanced by a factor of 1.5 to 1.75. The reduced enzyme is readily reoxidized by dioxygen, ferricyanide or hydrogen peroxide. It binds two molecules of hydrogen peroxide in the oxidized state (1/type-3 Cu pair), which can be monitored by a characteristic increase of the absorbance around 310 nm (delta epsilon = 1000 +/- 50 M-1 cm-1). Corresponding changes in EPR and fluorescence spectra have not been detected.

Amino Acids↗
PubMed1979

Mavicyanin, a blue copper protein from Cucurbita pepo medullosa. Purification and characterization.

1. The copper protein mavicyanin has been isolated and purified from the green squash Cucurbita pepo medullosa. 2. Mavicyanin contains one type-1 copper/18000 Mr, which can be characterized by: intense absorption maximum at 600 nm (epsilon = 5000 M-1 cm-1/Cu, A280/A600 = 8.0 +/- 0.5, A600/A403 = 7.0 +/- 0.25, maximum of fluorescence emission at 335 nM. 3. In the oxidized state the copper of mavicyanin is 100% detectable by electron paramagnetic resonance (EPR). Computer simulation of the rhombic EPR signal gives gz = 2.287, gy = 2.077, gx = 2.025, Az = 3.5 mT, Ay = 2.9 mT and Ax = 5.7 mT. 4. Like other simple type-1 copper proteins, such as stellacyanin, azurin or plastocyanin, mavicyanin is readily reduced by hydroquinone or L-ascorbic acid. Its midpoint potential E'm was determined to be + 285 mV. The reduced protein reacts rather slowly with dioxygen, but is rapidly reoxidized by ferricyanide.

Amino Acids↗
PubMed1977

Evidence about the catecholoxidase activity of the enzyme ascorbate oxidase extracted from Cucurbita pepo medullosa.

Pure ascorbate oxidase (L-ascorbate:oxygen oxidoreductase, EC 1.10.3.3) isolated from Cucurbita pepo medullosa, which is known to be specific for ascorbic acid, shows a secondary catecholoxidase activity at approx. pH 6.7. This activity was tested against natural and synthetic compounds possessing a catechol-like structure. Among natural compounds (+)-catechin furnishes the same complex oxidation mixture obtained with other oxidases. Among synthetic compounds, 3,5-di-t-butylcatechol and 4-t-butylcatechol give the corresponding o-quinones. The significance of this secondary activity in the darkening process of fruits and vegetables which contain ascorbate oxidase is also discussed.

Ascorbate Oxidase↗
PubMedDate not supplied

Vanadate as an inhibitor of plant and mammalian peroxidases.

Vanadate ions are shown to inhibit horseradish, squash, and rat intestinal peroxidases by following the reaction spectrophotometrically in a wide range of vanadate concentrations. I50 in phosphate buffer were 43, 9.4, and 535 microM, respectively. No inhibitory effect was found on cow milk lactoperoxidase and beef liver catalase. Gel filtration of peroxidases in the presence of vanadate, as carried out by radioactive 48V for horseradish peroxidases (either in aerobic or anoxic conditions) and neutron activation analysis (NAA) for squash peroxidase, demonstrated a binding of vanadium to these enzymes in stoichiometric amounts. Electron paramagnetic resonance spectra of the eluted peaks for the former peroxidase indicated that vanadium is in the +5 oxidation state, but an equilibrium between V (V) and V (IV) in the assay conditions cannot be discarded. Although the inhibitory mechanism remains obscure, some hypotheses are considered. The potential implications that the inhibitory effect of vanadium might have on plant and animal metabolism are also discussed.

Animals↗