scholarly journals Alloxan-diabetes alters kinetic properties of the membrane-bound form, but not of the soluble form, of acetylcholinesterase in rat brain

1995 ◽  
Vol 307 (3) ◽  
pp. 647-649 ◽  
Author(s):  
M A Khandkar ◽  
E Mukherjee ◽  
D V Parmar ◽  
S S Katyare
Keyword(s):  
Rat Brain ◽  
Alloxan Diabetes ◽  
Membrane Binding ◽  
Soluble Form ◽  
Control Group ◽  
Kinetic Properties ◽  
Diabetic State ◽  
Membrane Bound

We examined the effects of alloxan-diabetes on the kinetic properties of the soluble and the membrane-bound forms of acetylcholinesterase (AChE) in rat brain. The Km (0.15 mM) and Vmax. (1.5 mmol/min per mg of protein) of the soluble form of the enzyme were unchanged in the diabetic animals. The membrane-bound enzyme in the control group displayed a lower Km (0.09 mM) and a higher Vmax. (7.2 mmol/min per mg of protein) compared with the soluble form of the enzyme; the diabetic state caused a significant increase (40%) in both Km and Vmax. Kis values were about 3-4 times higher for the membrane-bound enzyme in both control and diabetic animals. The results suggest that membrane binding and membrane alterations in diabetes can significantly influence the kinetic properties of AChE.

Effect of Alloxan-Diabetes and Subsequent Treatment with Insulin on Kinetic Properties of Succinate Oxidase Activity from Rat Liver Mitochondria

2006 ◽  
Vol 61 (9-10) ◽  
pp. 756-762 ◽  
Author(s):  
Samir P. Patel ◽  
Surendra S. Katyare
Keyword(s):  
Rat Liver ◽  
Alloxan Diabetes ◽  
Insulin Treatment ◽  
Liver Mitochondria ◽  
Subsequent Treatment ◽  
Rat Liver Mitochondria ◽  
Kinetic Properties ◽  
Diabetic State ◽  
The One ◽  
Succinate Oxidase

AbstractWe evaluated early and late effects of alloxan-diabetes and subsequent insulin treatment on the kinetic properties of succinate oxidase (SO) in rat liver mitochondria. Diabetic state lowered the SO activity; insulin treatment was effective in restoring the activity only in oneweek diabetic rats. The energies of activation in low and high temperature ranges (EH and EL) decreased significantly in diabetic animals; once again insulin treatment was partially effective only in the one-week diabetic group. The total phospholipids (TPL) and cholesterol (CHL) contents did not change in one-week groups. In one-month diabetic animals TPL decreased while CHL increased; insulin treatment induced further changes without restoring normality. The lysophospholipid (Lyso), sphingomyelin (SPM), phosphatidylinositol (PI) and phosphatidylserine (PS) content increased in the diabetic state while phosphatidylcholine (PC) and phosphatidylethanolamine (PE) decreased. Insulin treatment had a partial restorative effect. The changes in EH correlated negatively with SPM. The phase transition temperature, Tt, decreased in diabetic and insulin-treated groups. These changes correlated positively with the ratios of TPL/PI and TPL/PS. The membrane fluidity decreased in the diabetic state; insulin had a restorative effect only in the one-week group.

scholarly journals Physical and kinetic properties of a plasma-membrane-bound β-d-glucosidase (cellobiase) from midgut cells of an insect (Rhynchosciara americana larva)

1983 ◽  
Vol 213 (1) ◽  
pp. 43-51 ◽  
Author(s):  
C Ferreira ◽  
W R Terra
Keyword(s):  
Plasma Membrane ◽  
Gradient Centrifugation ◽  
Soluble Form ◽  
Kinetic Properties ◽  
Carbonium Ion ◽  
Wide Range ◽  
Catalytic Constant ◽  
Rhynchosciara Americana ◽  
Membrane Bound ◽  
Triton X

The midgut caecal cells from Rhynchosciara americana larvae possess a plasma-membrane-bound beta-D-glucosidase (cellobiase, EC 3.2.1.21), which is recovered (75-95%) in soluble form both after treatment with Triton X-100 and after treatment with papain. The Triton X-100-solubilized beta-D-glucosidase displays Mr106000 and pI 5.4, whereas the papain-released beta-D-glucosidase shows Mr65000 and pI 4.7. Thermal inactivations of the detergent-solubilized and the papain-released forms of beta-D-glucosidase both follow apparent first-order kinetics with similar half-lives. The papain-released beta-D-glucosidase, after being purified by density-gradient centrifugation, hydrolyses beta-D-glucosides, beta-D-galactosides and beta-D-fucosides at the same active site, as inferred from experiments of competition between substrates. The beta-D-glucosidase seems to operate in accordance with rapid-equilibrium kinetics, since the Km (0.61 mM) for the enzyme is constant over a wide range of pH. The hydrolysis of the beta-D-glucosidic bond catalysed by the beta-D-glucosidase occurs without inversion of configuration, delta-gluconolactone is a strong (Ki 0.5 microM) inhibitor of the enzyme and substituents in the substrate aglycone affect the catalytic constant of the reaction. These data support the assumption that the mechanism of the reaction catalysed by the beta-D-glucosidase involves the intermediary formation of a carbonium ion, rather than a glucosyl-enzyme intermediate.

Tissue Cholinesterases. A Comparative Study of Their Kinetic Properties

2000 ◽  
Vol 55 (1-2) ◽  
pp. 100-108 ◽  
Author(s):  
Kunjan R. Dave ◽  
Anshu R. Syal ◽  
Surendra S. Katyare
Keyword(s):  
Human Serum ◽  
Erythrocyte Membranes ◽  
Soluble Form ◽  
Kinetic Properties ◽  
Rat Serum ◽  
Human Erythrocyte Membranes ◽  
Substrate Saturation ◽  
Membrane Bound ◽  
The One ◽  
Three Components

Abstract The substrate saturation and temperature-dependent kinetic properties of soluble and membrane-bound forms of acetylcholinestarase (AChE) from brain and butyrylcholinesterase (BChE) from heart and liver were examined. In simultaneous studies these parameters were also measured for AChE in erythrocyte membranes and for BChE in the serum from rat and humans. For both soluble and membrane-bound forms of the enzyme from the three tissues, two components were discernible. In the brain, Km of component I (high affinity) and component II (low affinity) was somewhat higher in membrane-bound form than that of the soluble form components, while the Vmax values were significantly higher by about five fold. In the heart, K m of component II was lower in membrane-bound form than in the soluble form, while Vmax for both the components was about four to six fold higher in the membrane-bound form. In the liver, Vmax was marginally higher for the two components of the membrane-bound enzyme; the Km only of component I was higher by a factor of 2. In the rat erythrocyte membranes three components of AChE were present showing increasing values of Km and Vmax. In contrast, in the human erythrocyte membranes only two components could be detected; the one corresponding to component II of rat erythrocyte membranes was absent. In the rat serum two components of BChE were present while the human serum was found to possess three components. Component I of the human serum was missing in the rat serum. Temperature kinetics studies revealed that the Arrhenius plots were biphasic for most of the systems except for human serum. Membrane binding of the enzyme resulted in decreased energy of activation with shift in phase transition temperature (Tt) to near physiological temperature.

Na+,K+-ATPase and Mg2+-ATPase Activities in Different Regions of Rat Brain During Alloxan Diabetes

1982 ◽  
Vol 39 (4) ◽  
pp. 903-908 ◽  
Author(s):  
C. S. K. Mayanil ◽  
S. M. I. Kazmi ◽  
N. Z. Baquer
Keyword(s):  
Rat Brain ◽  
Alloxan Diabetes

scholarly journals Membrane Interactions of the Tick-Borne Encephalitis Virus Fusion Protein E at Low pH

2002 ◽  
Vol 76 (8) ◽  
pp. 3784-3790 ◽  
Author(s):  
Karin Stiasny ◽  
Steven L. Allison ◽  
Juliane Schalich ◽  
Franz X. Heinz
Keyword(s):  
Fusion Protein ◽  
Membrane Binding ◽  
Low Ph ◽  
Encephalitis Virus ◽  
Soluble Form ◽  
Viral Fusion ◽  
Sequence Element ◽  
Viral Fusion Protein ◽  
Tick Borne Encephalitis ◽  
Tick Borne Encephalitis Virus

ABSTRACT Membrane fusion of the flavivirus tick-borne encephalitis virus is triggered by the mildly acidic pH of the endosome and is mediated by envelope protein E, a class II viral fusion protein. The low-pH trigger induces an oligomeric rearrangement in which the subunits of the native E homodimers dissociate and the monomeric subunits then reassociate into homotrimers. Here we provide evidence that membrane binding is mediated by the intermediate monomeric form of E, generated by low-pH-induced dissociation of the dimer. Liposome coflotation experiments revealed that association with target membranes occurred only when liposomes were present at the time of acidification, whereas pretreating virions at low pH in the absence of membranes resulted in the loss of their ability to stably attach to liposomes. With the cleavable cross-linker ethylene glycolbis(succinimidylsuccinate), it was shown that a truncated soluble form of the E protein (sE) could bind to membranes only when the dimers were free to dissociate at low pH, and binding could be blocked by a monoclonal antibody that recognizes the fusion peptide, which is at the distal tip of the E monomer but is buried in the native dimer. Surprisingly, analysis of the membrane-associated sE proteins revealed that they had formed trimers. This was unexpected because this protein lacks a sequence element in the C-terminal stem-anchor region, which was shown to be essential for trimerization in the absence of a target membrane. It can therefore be concluded that the formation of a trimeric form of sE is facilitated by membrane binding. Its stability is apparently maintained by contacts between the ectodomains only and is not dependent on sequence elements in the stem-anchor region as previously assumed.  

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