phenylalanine-methyl-ester and leucine-methyl-ester

Three new amino acid derivatives, oxalamido-L-phenylalanine methyl ester (1), oxalamido-L-leucine methyl ester (2), and lumichrome hydrolyzate (3), together with nine known compounds (4-12), were isolated from the solid culture of edible mushroom Pleurotus ostreatus. Their structures were elucidated on the basis of extensive spectroscopic analysis. The absolute configurations of 1 and 2 were established by the chiral synthesis and confirmed by circular dichroism (CD) analysis of their total synthesis products and natural isolates. All new compounds were evaluated for their antioxidant effects, antimicrobial activities, and cytotoxic activity. Compounds 1-3 showed weak antifungal activities against Candida albicans with minimum inhibitory concentration (MIC) value of 500 μg/ml.

Topics: Agaricales; Antioxidants; Candida albicans; Flavins; Leucine; Microbial Sensitivity Tests; Molecular Structure; Phenylalanine; Pleurotus

L-leucine methyl ester (Leu-OMe), Leu-Leu-OMe, Phe-OMe, and Glu-(OMe)2 are toxic to mononuclear phagocytes (M phi) and neutrophils. In the present studies, the mechanism of this toxicity was examined. A concentration of NH4Cl known to neutralize lysosomal pH and to block conversion of Leu-OMe to the dipeptide condensation product Leu-Leu-OMe inhibited Leu-OMe- or Glu-(OMe)2- but not Leu-Leu-OMe-mediated M phi toxicity. Leu-OMe-, Glu-(OMe)2-, or Leu-Leu-OMe-mediated killing of M phi was prevented by Gly-Phe-CHN2, a specific inhibitor of the thiol protease, dipeptidyl peptidase I (DPPI). Neither NH4Cl nor Gly-Phe-CHN2 prevented Phe-OMe-mediated M phi toxicity. In contrast, inhibition of M phi serine esterase activity prevented Phe-OMe- but not Leu-OMe- or Glu-(OMe)2-mediated killing of M phi. The myeloid tumor lines U937, HL60, and THP-1 were found to be uniformly enriched in DPPI and susceptible to Leu-Leu-OMe but not Leu-OMe toxicity. Whereas HL60 were resistant to Phe-OMe, THP-1 cells were killed by this agent. Incubation of peripheral blood mononuclear cells with Leu-OMe resulted in loss of natural killer (NK) functions and cytotoxic T lymphocytes (CTL) precursors, a process that requires the DPPI-dependent generation of membranolytic polymerization products. Phe-OMe had no toxic effects on NK cells or CTL precursors. These results indicate that Leu-OMe and Glu-(OMe)2 toxicity for M phi is related to the production of higher molecular weight hydrophobic polymerization products via the sequential action of two nonserine esterase lysosomal enzymes. In contrast, Phe-OMe toxicity for myeloid cells was found to correlate with serine esterase-mediated intracellular trapping of high concentrations of the free amino acid Phe. These distinct enzymatic mechanisms may provide a unique means of targeting agents capable of selectively deleting cells of myeloid lineage.

Topics: Adult; Ammonium Chloride; Cathepsin C; Cell Death; Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; Esterases; Glutamates; Granulocytes; Humans; Killer Cells, Natural; Leucine; Leukemia, Myeloid; Leukocytes, Mononuclear; Neutrophils; Phagocytes; Phenylalanine; T-Lymphocytes, Cytotoxic; Tumor Cells, Cultured

Culture of human peripheral blood mononuclear cells with purified interleukin 2 (IL-2) results in the induction of a cytotoxic population of cells capable of lysing autologous tumor cells and natural killer (NK) cell resistant tumor cell lines. The current study was undertaken to characterize biological agents which might modulate the induction of lymphokine (IL-2) activated killer (LAK) cells and to optimize culture conditions for LAK cell induction. Preliminary studies were undertaken to characterize optimal time and IL-2 concentration for induction of LAK cell activity. Subsequently, we demonstrated that: (a) LAK cell induction is inhibited at high (2.5 X 10(6)/ml) cell concentrations and this phenomenon is due to the presence of monocytes; (b) depletion of monocytes allows LAK cell induction at 5-10-fold higher cell concentrations without altering the extent or range of LAK-cell activity; (c) interleukin 1 enhances and alpha- and beta-interferons inhibit IL-2 induced proliferation, without altering LAK cell induction; and (d) gamma-interferon alters neither IL-2 induction of proliferation nor LAK cell activity.

Topics: Cytotoxicity, Immunologic; Humans; Interferons; Interleukin-1; Interleukin-2; Killer Cells, Natural; Kinetics; Leucine; Monocytes; Phenylalanine; Thymidine; Tritium

Perfusion of rat hearts as Langendorff preparations for 20 min with buffer containing 15 mM glucose and either 10 mM methionine methyl ester or 10 mM leucine methyl ester decreased 1) latency of beta-N-acetylglucosaminidase, 2) buoyant density of cardiac lysosomes, 3) the rate of proteolysis, and 4) heart rate and coronary flow. A significant inhibitory effect on proteolysis was not observed during this brief exposure of insulin-treated hearts to the methyl esters. The effects of the methyl esters were reversible when they were washed away. Heart rate and coronary flow returned to control values within 5 min. After 90 min of recovery, lysosomes distributed on Percoll gradients in dense and buoyant bands that were indistinguishable from control hearts. The reversibility of these effects correlated with the net release of either methionine or leucine from hearts exposed to the corresponding methyl ester. During recovery, rates of proteolysis returned toward those observed in control hearts. In insulin-treated hearts, methionine methyl ester inhibited proteolysis during the recovery period, but leucine methyl ester had no effect. These results indicate that exposure to amino acid methyl esters led to swelling of cardiac lysosomes and inhibition of protein degradation. These effects appeared to be related to the amount of free amino acid that was retained.

Topics: Adenosine Triphosphate; Amino Acids; Animals; Glucose; Heart; Insulin; Leucine; Lysosomes; Male; Methionine; Myocardium; Phenylalanine; Proteins; Rats; Rats, Inbred Strains