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V Talesa

Publications and source records attributed to V Talesa.

36 records · Page 2Linked to original sources
PubMed1990

Induction of mouse liver glyoxalase I by hypobaric hypoxia.

Hypobaric hypoxia at 0.45 atm induced a reversible increase of mouse liver glyoxalase I. The levels of this enzyme increased after an exposure of 20 h and 20 + 20 h, whereas the activity decreased to the control values after 20 h at room pressure. Before the treatment, some animals received tritiated leucine (i.p.). Glyoxalase I was purified to homogeneity. The pure enzyme from the treated animals showed 20-times more radioactivity than the controls. Thus, the increase in specific activity is due to new protein synthesized in response to the treatment at 0.45 atm. The activities of glyoxalase II and glutathione S-transferase were not affected by the treatment.

Animals↗
PubMed1989

Isolation of glyoxalase II from two different compartments of rat liver mitochondria. Kinetic and immunochemical characterization of the enzymes.

Two separate pools of glyoxalase II were demonstrated in rat liver mitochondria, one in the intermembrane space and the other in the matrix. The enzyme was purified from both sources by affinity chromatography on S-(carbobenzoxy)glutathione-Affi-Gel 40. From both crude and purified preparations polyacrylamide gel-electrophoresis resolved multiple forms of glyoxalase II, two from the intermembrane space and five from the matrix. Among the thioesters of glutathione tested as substrates, S-D-lactoylglutathione was hydrolyzed most efficiently by the enzymes from both sources. Significant differences were observed in the specificities between the intermembrane space and matrix enzymes with S-acetoacetylglutathione, S-acetylglutathione, S-propionylglutathione and S-succinylglutathione as substrates. Pure glyoxalase II from rat liver cytosol was chemically polymerized and used as antigen. Antibodies were raised in rabbits and the antiserum was used for comparison of the two purified mitochondrial enzymes with cytosolic glyoxalase II by immunoblotting. The enzyme purified from the intermembrane space cross-reacted with the antiserum, but the matrix glyoxalase II did not. The results give evidence for the presence in rat liver mitochondria of two species of glyoxalase II with differing characteristics. Only the enzyme from the intermembrane space appears to resemble the cytosolic glyoxalase II forms.

Animals↗
PubMed1989

Glyoxalase II from Zea mays: properties and inhibition study of the enzyme purified by use of a new affinity ligand.

The synthesis of N-(p-nitrocarbobenzoxy)glutathione (N-pNCBG) is reported. N-pNCBG and glutathione (GSH) were coupled to Affi-gel 10 by a thioester linkage and resulted in very effective bound ligands for a fast purification of glyoxalase II from corn. The S-(N-pNCBG)-affinity column showed a glyoxalase II binding capacity of up to 2-fold higher than that of the glutathione-affinity column. A single form of glyoxalase II was evidenced by PAGE in both crude extracts and in the affinity purified enzyme. A 45% recovery of glyoxalase II activity (purification, approx. 433-fold) was obtained for both matrices by a single chromatography. The purified glyoxalase is an acidic protein (pI 4.5) of about 26,000 relative molecular mass. Substrate studies for the corn glyoxalase II show, among possible substrates tested, that S-D-lactyl-glutathione is the preferred substrate. An inhibition study was performed with methyl-, propyl-, hexyl-, p-nitrobenzyl-, p-chlorophenacyl-, carbobenzoxy-, and p-nitrocarbobenzoxy-S-glutathione. Methyl-S-glutathione did not inhibit corn glyoxalase II; the others were found to be linear competitive inhibitors. The derivatives containing a thioether bond are weaker inhibitors than those containing a thioester bond or a carbonyl group. p-Nitrobenzyl-S-glutathione is the weakest inhibitor; the carbobenzoxy-S-derivatives are stronger inhibitors than the p-chlorophenacyl S-derivative.

Chromatography, Affinity↗
PubMed1989

Effects of some S-blocked glutathione derivatives on the prevalent glyoxalase II (a form) of rat liver.

The prevalent glyoxalase II (S-2-hydroxyacylglutathione hydrolase, EC 3.1.2.6, a form) of rat liver cytosol has been studied with a series of seven S-blocked glutathione derivatives. At pH 7.4 and 20 degrees C, only p-nitrobenzyl-S-glutathione was found completely inactive. All the other derivatives are linear competitive inhibitors of the enzyme. Ki values using S-D-lactoylglutathione as substrate are reported. Alkyl-S-glutathiones are weak inhibitors and their inhibition increases with the decrease of the length of the alkyl chain. The best inhibitors are those glutathione derivatives which contain a thioester bond (carbobenzoxy- and p-nitrocarbobenzoxy-S-glutathione) or a carbonyl group (p-chlorophenacyl-S-glutathione). Inhibition by carbobenzoxy-S-glutathione seems to be more complex since the double reciprocal plot shows deviation from linearity at low substrate concentration.

Animals↗
PubMed1988

Demonstration of glyoxalase II in rat liver mitochondria. Partial purification and occurrence in multiple forms.

Glyoxalase II (S-(2-hydroxyacyl)glutathione hydrolase, EC 3.1.2.6), which has been regarded as a cytosolic enzyme, was also found in rat liver mitochondria. The mitochondrial fraction contained about 10-15% of the total glyoxalase II activity in liver. The actual existence of the specific mitochondrial glyoxalase II was verified by showing that all of the activity of the crude mitochondrial pellet was still present in purified mitochondria prepared in a Ficoll gradient. Subfractionation of the mitochondria by digitonin treatment showed that 56% of the activity resided in the mitochondrial matrix and 19% in the intermembrane space. Partial purification of the enzyme (420-fold) was also achieved. Statistically significant differences were found in the substrate specificities of the mitochondrial and the cytosolic glyoxalase II. Electrophoresis and isoelectric focusing of either the crude mitochondrial extract or of the purified mitochondrial glyoxalase II resolved the enzyme activity into five forms with the respective pI values of 8.1, 7.5, 7.0, 6.85 and 6.6. Three of these forms (pI values 7.0-6.6) were exclusively mitochondrial, with no counterpart in the cytosol. The relative molecular mass of the partially purified enzyme, as estimated by Superose 12 gel chromatography, was 21,000. These results give evidence for the presence of mitochondrial glyoxalase II which is different from the cytosolic enzymes in several characteristics.

Animals↗
PubMed1987

Purification and characterization of two forms of glyoxalase II from the liver and brain of Wistar rats.

Glyoxalase II (S-(2-hydroxyacyl)glutathione hydrolase, EC 3.1.2.6) was purified to homogeneity and separated into two forms (alpha, pI = 8.0; beta, pI = 7.4) from both liver and brain of wistar rats by column isoelectric focusing. These forms were also found to have different electrophoretic mobilities. No significant differences were found between the alpha and beta forms from either source in the relative molecular mass (about 24,000) or in Km values using three substrates. The temperature-inactivation profiles were also similar, the two forms being stable up to 50 degrees C. Chemical modification studies with phenylglyoxal suggest that these enzyme forms probably contain arginine residues near the active site. Inactivation of alpha and beta forms by diethylpyrocarbonate and by photooxidation with methylene blue, and protection by S-D-mandeloylglutathione, a slowly reacting substrate, suggest the presence of histidine at the active site. The alpha and beta forms show different half-life values in inactivation by histidine reagents, which may be due to a difference in the active-site structures of these enzymes. The results probably indicate distinct structures (sequences) for alpha and beta forms.

Animals↗
PubMed1987

A comparative study on glyoxalase II from vertebrata.

S-2-hydroxyacylglutathione hydrolase (glyoxalase II) from the liver of animals belonging to the various vertebrate classes (Oryctolagus cuniculus, Gallus gallus, Python molurus, Rana esculenta, Esox lucius) have been purified from 100,000 g supernatants of liver homogenates, using acetone fractionation and affinity chromatography. Subsequent comparative studies were concerned with some molecular and kinetic properties. Isoelectric focusing gave evidence for a single form of liver glyoxalase II in O. cuniculus, P. molurus and E. lucius, while the enzyme from G. gallus and R. esculenta showed respectively two and three forms with different pI values. All studied enzymes are basic proteins. The relative molecular mass values range from 18,000 to 23,000. The various glyoxalases II do not display markedly different Kn or Ki values. Their stability behavior at different temperatures is also quite similar.

Animals↗
PubMed1985

Alkaline phosphatase in Hirudo medicinalis L.: partial purification and study of certain molecular and catalytic properties.

The authors carried out extraction and purification of an alkaline phosphatase (AP) from Hirudo medicinalis and studied certain characteristics of the enzyme. After homogenizing specimens of H. medicinalis and centrifuging the homogenate at 70,000 g, the enzyme, likely membrane-bound, was obtained in a soluble form by treating the sediment with n-butanol. It was then purified by acetone fractionation and Sephadex G-200 chromatography. A fairly good purification degree was achieved; the enzyme appears to be in a single form and displays a molecular weight of about 268,000. The optimum pH (9.5) is lower than the ones generally observed as regards APs from both Invertebrata and Mammalia. The studied AP displays a strong substrate inhibition, similar to that concerning Metazoa at a higher evolutionary level (Mollusca, Echinodermata). On the contrary, the enzyme-substrate affinity, as shown by Km value (2.447 mM), is lower than as regards APs from more advanced organisms (Echinodermata, Mammalia).

Alkaline Phosphatase↗
PubMed1985

Influence of sexual hormones on solid tumor growth and ATP C+ cell replication.

Solid tumors obtained by implanting ATP C+ cells subcutaneously into the back of BALB/cf/Had/Se substrain mice developed more rapidly in males than females. Experiments conducted on gonadectomized animals demonstrated that female gonads inhibit the development of this tumor. Studies on ATP C+ cells cultured in vitro with various doses of male and female hormones showed that mainly progesterone, but to a lesser extent also estradiol, significantly inhibit cell proliferation with respect to testosterone. The treatment of normal and gonadectomized animals with testosterone and progesterone confirms the results obtained in vitro. Analyses carried out on ATP C+ cells do not reveal presence of estradiol and progesterone receptors.

Animals↗
PubMed1985

Effect of ascorbic and dehydroascorbic acid on glyoxalase enzyme system.

The authors studied the effect of ascorbic and dehydroascorbic acid on glyoxalase enzyme system, in order to establish if these substances influence cell proliferation by interfering with glyoxalase activity. The results demonstrate that both ascorbic and dehydroascorbic acid do not alter glyoxalase activity in vitro, even if employed at high doses.

Animals↗
PubMed1984

Effects of ascorbic and dehydroascorbic acid on the multiplication of tumor ascites cells in vitro.

The effects of AA and DHA on ATP C+ cell multiplication in vitro were studied by measuring incorporation of 3H thymidine into DNA. The results obtained demonstrate that both AA and DHA have the same effects: they favor cell multiplication at low doses and inhibit it at high doses. Experiments carried out with serial doses of both these substances revealed that AA is more efficient in determining both stimulating and inhibiting effects. The lesser efficiency of DHA may be attributed to its limited stability in culture medium. Studies on the effect of high doses of AA and DHA added to the culture medium in single or fractionated doses revealed that fractionated administration is more efficient in inhibiting cell multiplication than single administration.

Animals↗
PubMed1984

Purification of S-2-hydroxyacylglutathione hydrolase (Glyoxalase II) from calf brain.

S-2-Hydroxyacylglutathione hydrolase (Glyoxalase II) from calf brain has been purified 8333-times compared to 65,000 g supernatant of brain homogenate. The purification procedure employs Affi-Gel blue and preparative isoelectric focussing and offers a suitable method for the preparation of highly purified enzyme. Calf brain Glyoxalase II is a basic protein with a pl of 7.63 determined by isoelectric focusing. An evaluation of the relative molecular mass by gel filtration gave a value of about 23,000. During the purification procedure a constant Km value of about 0.325 mM was observed. A turnover number of 16,100 min-1 was calculated for the purified enzyme.

Animals↗
PubMed1983

Stimulating effect of ascorbic acid on ascites tumor cell multiplication in vitro.

In a preceding report evidence has been presented that ascorbic acid (AA) accelerated solid tumor growth obtained by inoculating tumor ascites cells into the subcutaneous dorsal region of inbred Balb/cf/Had/Se substrain mice. The present work investigates whether this effect is the result of a direct action of AA on neoplastic cell multiplication or of an indirect action on the tumor cells mediated by changes induced by AA in the organism bearing the tumor. The results obtained demonstrate that AA at low doses (microgram 10-30/ml) stimulates ascites tumor cell multiplication in vitro, while at high doses (microgram 60-120/ml) the opposite occurs. These results suggest that the major growth of solid tumors observed in mice treated with AA may be attribute to the capacity of this substance to favor the multiplication of ATP cells which were used to induce the tumors.

Animals↗
PubMed1983

Absence of accumulation phenomena in normal and tumoral tissues of mice treated with ascorbic acid.

The authors studied the effects of an energetic and prolonged ascorbic acid (AA) treatment on AA concentration in a solid tumor obtained by transplanting ascites tumor cells in the dorsal subcutaneous region of Balb/C1/Had/Se substrain mice. The results demonstrate that this tumor, whose growth is favored by AA, not only is incapable of accumulating AA, but surprisingly presents a lowering of its concentration as the result of treatment with very high doses of AA. The levels of AA in various organs and tissues of mice bearing the aforesaid tumor show no significant difference to those observed in organs and tissues of healthy mice. An energetic and prolonged treatment with AA not only is incapable of favoring accumulation, but also causes a lowering of its concentration in the liver and kidney, similar to that observed in tumors. Therefore, the hypothesis may be advanced that this decrease is caused by the adaptation of some enzymatic system, which results in a greater utilization of AA. This greater consumption could be the cause of the decreased AA levels once esogenous administration is arrested.

Animals↗
PubMed1983

Activity changes of glyoxalases I-II and glutathione reductase in regenerating rat liver.

In regenerating rat liver Glyoxalase I activity shows a significant increase 24-48 hrs after partial hepatectomy. Glyoxalase II activity is significantly increased at 16, 48, and 72 hrs, and shows a transient decrease at 24 hrs after surgery. It is likely that the observed changes in Glyoxalases I and II activities during hepatic regeneration are correlated with the different roles of these enzymes. Glutathione reductase activity, significantly reduced within 8-72 hrs after surgery, does not show any correlation with Glyoxalases. These studied enzyme activities do not display significant changes in the sham-operated animals.

Animals↗