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The role lipid phase structure in the interaction of lactate dehydrogenase with phosphatidylserine. Activity studies.
Cell. Mol. Biol. Lett. 2002: 7 (3) s.895-903, il., bibliogr. 27 poz.
Lactate dehydrogenase is one of the enzymes of the glycolytic path. It has been shown to be able to bind in vitro to cellular membranes. The presence of anionic phospholipids induces changes in the catalytic properties of the enzyme similar to those found when the enzyme is bound to natural membranes. In this study, a nonionic detergent (Tween 20), at concentrations not affecting the catalytic activity of LDL, was used to study the role of the lipid supra-molecular structure in the interaction between pig skeletal muscle lactate dehydrogenase and phosphatidylserine. Tween 20 changes the equilibrium of concentrations between the lipid supra-molecular forms. The detergent at ther used concentration values did not alter the activity of the enzyme when it was used on its own, but did diminsh the level of inhibition induced by the studied phospholipid. The obtained results showed that the interaction is reversible and that the bilayer structure of the lipid is essential for the inhibition.
Further evidence for the importance of lipid bilayers in the interaction between lactate dehydrogenase and phosphatidylserine.
Cell. Mol. Biol. Lett. 2002: 7 (3) s.905-910, il., bibliogr. 14 poz.
Lactate dehydrogenase (LDH) is one of the glycolytic enzymes, which have been proved to have the capibility to reverse non-specific adsorption on cellular membranous structures in vitro, as well as on the structural proteins of the contractile system of muscle cells. It has been suggested that this binding may play a physiological role, as it alters the enzyme's kinetic properties. Our previous studies on this enzyme showed that its interaction with some anionic phospholipids reveals similar characteristics and similar effect on the activity of the enzyme to those ehich had been observed for the interaction with membranous structures. Disruption of the lipid bilayers by nonionic detergent (Tween 20) restored the enzyme activity inhibited by the presence of phosphatidylserine (PS) liposomes. In this study, we used the measurement of enzyme tryptophanyl fluorescence spectra to monitor the interaction andf possible changes in the enzyme conformation. The investigation provided further evidence of the importance of the bilayer structure in this interaction. Similarly to the effect on the activity of the enzyme, the addition of Tween 20 diminishes the quenching of the LDH tryptophanyl fluorescence, and finally completely restores the fluorescence.
Activity of cysteine proteases and their inhibitors in the lymph nodes of larynx cancer patients.
Med. Sci. Monitor 2002: 8 (12) s.BR540-BR544, tab., bibliogr. 32 poz.
Hasła klasyfikacyjne GBL:
Background: Cysteine endopeptidases and their inhibitors play an important role in the process of carcinogenesis. Positive correlation has been found between tumor invasiveness, its metastatic potential and the secretion of cyseine endopepetidases. Cysteine protease inhibitory activity is also altered in malignant tumors and various body fluids of patients with cancer. Material and methods: Total cysteine endopeptidase activity and cysteine proteinase inhibitory activity were measured in homongenates of cervical lymph node tissue surgically obtained from the larynx of cancer patients. The tissue samples were histologically examined, and each was divided into two parts: positive (PCN), with mostly cancer cells, and negative (NCN) with no cancer cells. Results: In the PCNs, the levels of the assayed enzymes and their inhibitors were significantly higher than in NCNs. The mean values of cysteine proteinase activity were 2.70 ń 2.29 and 1.59 ń 1.28 for PCNs and NCNs, respectively (p 0.005). The mean values of cysteine protease inhibitors were 9.1 ń 8.6 and 6.1 ń 6.3 for PCNs and NCNs, respectively (p 0.02). An altered protease-inhibitor activity ratio was also found in PCN samples compared to NCNs. Conclusions: These data suggest increased activity of cysteine peptidases and their inhibitors in the case of secondary tumor tissue. The cancer cells metastasized to lymph node tissue produce some alteration in balance between cysteine protease activity and the endogenous inhibitors of the proteases.
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