8-Methoxypsoralen potentiates the photocytotoxic effect of Photofrin II towards EMT-6 murine tumor cells.

Pretreatment of EMT-6 murine tumor cells for 24 h with 10(-4) M 8-methoxypsoralen (8-MOP) increased the photocytotoxicity of Photofrin II (P2) after cell exposure to low doses (1-1.5 J/cm2) of UVA by two- to three-fold. 8-MOP alone had no cytotoxic action under these experimental conditions and did not significantly change the amount of P2 recovered in cells. 8-MOP enhanced the lipid peroxidation end product formation measured as thiobarbituric acid reactive substances (TBARS) during cell photosensitization by P2. The psoralen alone also slightly increased the TBARS level after UVA exposure. These results suggest that 8-MOP, albeit non-photocytotoxic by itself under our experimental conditions, could enhance the efficiency of P2 by increasing cellular lipid peroxidation following light exposure.

Effects of arginine butyrate and tributyrylxylitol on cultured human sarcoma cells.

The effects of arginine butyrate and tributyrylxylitol were studied comparatively in a human sarcoma cell line. Both induced important structural and functional modifications suggestive of cell differentiation, as shown by the dose-dependent increase of alkaline phosphatase activity and total protein content, at concentrations ranging from 1mM to 5 mM expressed in butyrate equivalents. hCG beta-subunit present in the culture medium increased with differentiation. Our results show that most of the differentiation changes previously reported for sodium butyrate in cancer cell lines are also produced by both drugs. Tributyrylxylitol appears to be the more potent and effective inducer of differentiation but its use is limited << in vitro >> on account of its relative toxicity at concentrations above 3 mM butyrate equivalents.

Swine liver L-leucine aminopeptidase: improved purification procedure.

An L-leucine aminopeptidase, having a specificity toward the substrate L-leucine amide, was purified 1084-fold from swine liver with a yield of 50.7 per cent. Purification procedure was carried out using successively centrifugation at 105 000 X g, fractionation by ammonium sulfate, DEAE Sephacel chromatography and zonal ultracentrifugation. Enzyme homogeneity and purity studies were carried out by analytical ultracentrifugation and polyacrylamide gel electrophoresis. In SDS-gel polyacrylamide, a single band was observed. It corresponded to a 55 000 molecular weight protein.

[Characterization of L-threonine deaminase activity of guinea pig liver induced by a high protein diet]. / Caractérisation de l'activité L-thréonine désaminasique du foie de cobaye induite par un régime hyperprotidique.

In a foregoing paper, we demonstrated that under equilibrated diet conditions, guinea pig liver L-threonine deaminase activity should be allocated to two distinct enzymes: a specific L-threonine deaminase without activity toward L-serine and a L-serine deaminase having a secondary activity toward L-threonine. In the present work, we observed that a high protidic diet caused an elevation of total threonine deaminase activity. Thus purification of guinea pig liver L-threonine deaminase was attempted, using ultracentrifugation, salt precipitation, heat treatment, ion exchange chromatography on DEAE Sephacel, Sephadex G 200 molecular sieve, 2 amino-2 methyl-1 propanol linked CH 4B Sepharose chromatography. The weak variations of the ratios of specific activities respectively toward L-threonine and L-serine observed at each stage of the purification procedure indicated that both activities are very likely supported by a single enzyme preexisting in the liver of guinea pigs fed an equilibrated diet. No isoenzyme was evidenced by polyacrylamide gel electrophoresis or DEAE Sephacel chromatography. Moreover, our purification procedure demonstrated that not only inducible L-threonine deaminase guinea pig liver activity was due to L-serine deaminase, but also that an initially existing specific L-threonine deaminase activity paradoxically disappeared with a protein rich diet.

Human liver L-leucine aminopeptidase: evidence for two forms compared to pig liver enzyme.

Two forms of L-leucine aminopeptidase (E.C. 3.4.11.1) having a specific activity toward L-leucine amide and L-leucylpeptides substrates but not toward chromogenic substrates: L-leucyl paranitroanilide or L-leucyl beta naphthylamide have been evidenced from human liver. Human liver enzymes have been distinguished from pig liver enzyme by DEAE Sephacel chromatography and analytical electrophoresis on cellulose acetate strips. We compared enzymic properties of L-leucine aminopeptidases from human liver with pig liver enzyme: they were activated by Mg2+ and Mn2+ and inhibited by Zn2+ and Co2+, EDTA and citric acid. The optimum pH's were 10. Both human liver L-leucine aminopeptidases were less sensitive to heat elevation than pig liver enzyme.

Purification and enzymatic properties of an L-leucine aminopeptidase from swine liver.

An L-leucine aminopeptidase (alpha-aminoacyl-peptide hydrolase (cytosol), EC 3.4.11.1), having a specificity toward the substrate L-leucine amide, but not toward L-leucyl beta-naphthylamide or L-leucyl p-nitroanilide, has been purified 332-fold from swine liver, with a yield of 8.6%. This is the first purification of this enzyme from hepatic tissue. The purified enzyme submitted to analytical electrophoresis on cellulose acetate strips or in polyacrylamide gel showed a single band after straining with Ponceau S Red dye or Amido black, respectively. Purified swine liver L-leucine aminopeptidase, a cytosol enzyme, exhibited a molecular weight of 268 000 +/- 50 000 by gel filtration. It hydrolyzed L-leucine amide substrate and L-leucyl peptides. It was activated by Mg2+ and Mn2+ and inhibited by Co2+ and Zn2+. The optimum pH was 10. It was rather sensitive to heat elevation. Swine liver L-leucine aminopeptidase was inhibited by EDTA, citric acid, isocaproic acid, dodecylamine, aliphatic alcohols and p-chloromercuribenzoate but unaffected by monoiodoacetic acid and diisopropyl fluorophosphate.

[Neutral leucinamidasic activity of human serum. Semiautomatic method of analysis]. / L'activité leucinamidasique neutre du sérum humain. Méthode de dosage semi-automatique.

Half automated method for determining a L-leucinamide splitting enzymatic activity in human sera. In normal and pathological human sera, two distinct L-leucinamide splitting enzymatic activities have been demonstrated. One of them has an optimal activity at pH 9 (alcaline leucine amidase activity) and shows the most properties of a classic leucinaminopeptidase (E.C. 3.4.11.1). The other (neutral leucine amidase activity) has an optimal activity at pH : 7,5--7,8 and is not activated by Mg2+ ions. In the present work a semi-automated method permitting the determination of the "neutral leucine amidase activity" is presented. The mean of the reference values for normal human sera are established to 31,54 mUI/ml, and the upper normal limit is 48 mUI/ml. The neutral leucine amidase activity is studied in pathological sera comparatively with two other aminopeptidase activities : "alcaline leucine amidase activity", and "leucine-arylamidase". Our study shows that in pathological sera, the neutral leucine amidase activity" varies often without any correlation with those parameters.