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1

Erythrocyte membrane [Ca2plus plus Mg2plus]-ATPase as affected by organophosphorus insecticides

100%
Blasiak J.
Polish Journal of Environmental Studies
|
1995
|
tom 04
|
nr 4
The organophosphorus insecticide bromfenvinfos (2-bromo-l-(2,4-dichlorophenyl)vinyl diethyl phosphate) and its methylated homologue methylbromfenvinfos inhibited noncompetitively the activity of (Ca2+ + Mg2+)-ATPase bound to and solubilized from pig erythrocyte membrane. Both enzyme preparations exhibited biphasic substrate curves displaying the existence of two functional active sites with low and high affinity to ATP. Inhibition of activity was more pronounced for bromfenvinfos than for methylbromfenvinfos and the solubilized enzyme preparation was more affected than the bound one. The results of the experiment suggest that the insecticides inhibited the ATPase by binding to a site on the enzyme rather than by interaction with associated lipids, although their presence could weaken the action of the compounds due to the stronger affinity of organophosphorus insecticides for lipids rather than for proteins.
2

The association of glycolytic enzymes with cellular and model membranes

100%
Gutowicz J., Terlecki G.
Cellular and Molecular Biology Letters
|
2003
|
tom 08
|
nr 3
This article deals with the binding of glycolytic enzymes with membranous or protein subcellular structures. The representative papers of the last three decades dealing with this matter are reviewed. The studies evidencing the binding of some glycolytic enzymes to insoluble subcellular proteins and membranous structures are presented. It is currently generally accepted that the glycolytic enzymes work in some organisation. Such organisation undoubtedly plays a marked role, although still poorly known, in the regulation processes of glycolysis. From this review, the conclusion emerges that the regulatory ability of the binding of glycolytic enzymes to cellular membranes should be added to the list of well-known mechanisms of post-translational regulation of the glycolytic enzymes. Some of the results presented are the background for the hypothesis that planar phospholipid domains in/on the membrane surface are capable of functioning as binding sites for these enzymes. Such binding can modify the conformation state of the enzymes, which results in changes in their kinetic properties; thus, it may function as a regulator of catalytic activity.
3

Paraquat-induced changes in the structure of erythrocyte membranes are not caused by lipid peroxidation

84%
Gwozdzinski K.
Current Topics in Biophysics
|
1994
|
tom 18
|
nr 2
4

Pink's model and lipid membranes

67%
Kubica K.
Cellular and Molecular Biology Letters
|
1997
|
tom 02
|
nr 3
The paper presents a discussion of the basic assumptions of the Pink's model, which is often used for interpreting phenomena connected with biological membranes. For over ten years now the model has been constantly developed, but its basic assumptions have not ever been evaluated, such as: constant value of surface pressure, independent of composition of the system studied; approximate value (120°) of the angle between -C-C- bonds in alkyl chains of the membrane molecules; or treating both lipid chains as identical and independent.
5

Inhibition of [Na a. K]-ATPase by organophosphorus insecticides

67%
Blasiak J.
Polish Journal of Environmental Studies
|
1995
|
tom 04
|
nr 1
The organophosphorus insecticide bromfenvinios and its methylated homologue methylbrom- fenvinfos inhibited the activity of pig kidney (Na++K+)-ATPase contained in the microsomal fraction and purified from it. The effect was dose-dependent Subrate kinetic studies of the enzyme revealed the existence of two active sites with high and low affinity to ATP respectively. The Dixon analysis of the mode of inhibition indicated its noncompetitive character. The inhibition was more pronouced for bromfenvinfos than for methylbromfenvinfos and the purified enzyme was more affected than the enzyme contained in the microsomal fraction. The Hill plot of inhibition indicated a multisite binding of both insecticides exhibiting cooperativity in binding. The Hill coefficient (n) fulfilled the relationship 1 < n < 3. These properties of the interaction suggest an allosteric nature of the inhibitory action of the insecticides. An indirect mechanism of the interaction was proposed: methylparathion could inhibit the activity of the (Na+ + K+)-ATPase by excluding the enzyme protein from its normal lipid milieu.
6

Ultracentrifugation studies of the location of the site involved in the interaction of pig heart lactate dehydrogenase with acidic phospholipids at low pH. A comparison with the muscle form of the enzyme

67%
Terlecki G., Czapinska E., Hotowy K.
Cellular and Molecular Biology Letters
|
2007
|
tom 12
|
nr 3
Lactate dehydrogenase (LDH) from the pig heart interacts with liposomes made of acidic phospholipids most effectively at low pH, close to the isoelectric point of the protein (pH = 5.5). This binding is not observed at neutral pH or high ionic strength. LDH-liposome complex formation requires an absence of nicotinamide adenine dinucleotides and adenine nucleotides in the interaction environment. Their presence limits the interaction of LDH with liposomes in a concentration-dependent manner. This phenomenon is not observed for pig skeletal muscle LDH. The heart LDH-liposome complexes formed in the absence of nicotinamide adenine dinucleotides and adenine nucleotides are stable after the addition of these substances even in millimolar concentrations. The LDH substrates and studied nucleotides that inhibit the interaction of pig heart LDH with acidic liposomes can be ordered according to their effectiveness as follows: NADH > NAD > ATP = ADP > AMP > pyruvate. The phosphorylated form of NAD (NADP), nonadenine nucleotides (GTP, CTP, UTP) and lactate are ineffective. Chemically cross-linked pig heart LDH, with a tetrameric structure stable at low pH, behaves analogously to the unmodified enzyme, which excludes the participation of the interfacing parts of subunits in the interaction with acidic phospholipids. The presented results indicate that in lowered pH conditions, the NADH-cofactor binding site of pig heart LDH is strongly involved in the interaction of the enzyme with acidic phospholipids. The contribution of the ATP/ADP binding site to this process can also be considered. In the case of pig skeletal muscle LDH, neither the cofactor binding site nor the subunit interfacing areas seem to be involved in the interaction.
7

Lipid-binding proteins as stabilizers of membrane microdomains - possible physiological significance

59%
Bandorowicz-Pikula J.
Acta Biochimica Polonica
|
2000
|
tom 47
|
nr 3
Below the melting point temperature of lipids, artificial lipid membranes usually exist in the ordered gel phase. Above these temperatures lipid acyl chains become fluid and disordered (liquid-crystalline phase). Depending on the chemical composition of artificial membranes, phase separation may occur, leading to the formation of transient or stable membrane domains. A similar phase separation of lipids into ordered and disordered domains has been observed in natural membranes at physiological temperature range. Moreover, it has been reported that certain proteins prefer certain organization of lipids, as for example glycosylphosphatidylinositol-anchored proteins or Src family of tyrosine kinases. The aim of present review is to discuss the possibility that some lipid microdomains are induced or stabilized by lipid-binding proteins that under certain conditions, for example due to a rise of cytosolic Ca2+ or pH changes, may attach to the membrane surface, inducing clustering of lipid molecules and creation of ordered lipid microdomains. These domains may than attract other cytosolic proteins, either enzymes or regulatory proteins. It is, therefore, postulated that lipid microdomains play important roles within a cell, in signal transduction and enzymatic catalysis, and also in various pathological states, as Alzheimer's disease, anti-phosphatidylserine syndrome, or development of multidrug resistance of cancer cells.
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