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Biomedical subjects

R K Banerjee

Publications and source records attributed to R K Banerjee.

At least 73 records · Page 4Linked to original sources
PubMed1983

Proteoliposome as the model for the study of membrane-bound enzymes and transport proteins.

Reconstitution of membrane-bound enzymes and transport proteins with the artificial phospholipid bilayer (liposomes) is one of the most useful techniques to study the functional aspects of these proteins. Several biochemical and biophysical parameters related to the expression of the functions of these proteins can be conveniently studied in the reconstituted proteoliposomes. Methods have been described for the preparation of model membranes and emphasis has been given specially to liposomes. Methodologies for the reconstitution of biologically active proteoliposomes using varieties of membrane-bound enzymes and proteins and their assay have been presented in details. The merits and demerits of each method and the subsequent modification of the technique have been indicated. Factors controlling the orientation and functions of the enzymes and carrier proteins in the reconstituted proteoliposomes have also been described. Attempts have been made to include few examples to describe how the reconstituted model membrane is helping us to know the molecular basis of many salient features of the biomembranes. Finally, the possible application of the proteoliposomes for the study of other complex membrane phenomena has been postulated.

Adenosine Triphosphatases↗
PubMed1981

Ecto-ATPase.

An ecto-adenosine triphosphatase (E.C. 3.6.1.4 ATP-phosphohydrolase) is shown to be localized on the outer surface of varieties of cell membrane. The enzyme is different from the ATPase involved in biological energy transduction and ion transport mechanism. The characteristic of the enzyme lies in having a very broad substrate specificity and is inhibited by EDTA and higher concentration of ATP. The enzyme is dependent on bivalent metal ions, Mg++ or Ca++ for its optimum activity. The enzyme is highly sensitive to SH-reagents but insensitive to inhibitors of mitochondrial ATPase or Na+- K+- ATPase. The possible functions of the enzyme in being oriented outside the cell membrane is discussed.

Adenosine Triphosphatases↗
PubMed1981

Gastric peroxidase--localization, catalytic properties and possible role in extrathyroidal thyroid hormone formation.

A highly active peroxidase (EC 1.11.1.7) has been found to be localized in the mitochondria isolated from the fundic region of mouse stomach. The stomach has also the property of concentrating iodide significantly. Evidence has been presented to show that the peroxidase is orientated outside the mitochondrial membrane. The enzyme is strongly inhibited by antithyroid drugs like methimazole and thiouracil. Azide and cyanide completely inactivate the enzyme. The activity is inhibited by SH-blocking reagents like mersalyl or p-chloromercuribenzene sulphonate, but not by N-ethyl-maleimide. The enzyme is also sensitive to the action of some proteolytic enzymes. It can catalyse the formation of mono- or diiodotyrosine from tyrosine or monoiodotyrosine as substrate, respectively. The enzyme is capable of synthesizing thyroxine and triiodothyronine on the backbone of a protein, such as thyroglobulin or albumin.

Animals↗
PubMed1980

Studies on peroxidase-catalysed formation of thyroid hormones on a protein isolated from submaxillary gland.

A protein has been solubilized and purified to homogeneity from the microsomal fraction of goat submaxillary gland. This protein can preferentially be iodinated to form triidothyronine and thyroxine with the help of submaxillary peroxidase (donor:hydrogen-peroxide oxidoreductase, EC 1.11.1.7) solubilized and purified from the same microsomal fraction. The protein can also be isolated from soluble supernatant and was found to be identical to the microsomal protein as judged by their moelcular properties as well as the formation of triiodothyronine and thyroxine. The protein has the molecular weight of 120 000 and contains two unequal subunits of molecular weight of 80 000 and 44 000. The molecular weight of the peroxidase is 72 000 and consists of a single polypeptide chain. The enzyme has the Rz value of 0.4 and is inhibited by azide and cyanide. Mersalyl, a mercurial, strongly inhibits the enzyme activity while N-ethylmaleimide cannot. The enzyme can catalyze the formation of 62 mumol of I3-/min per mg of protein at its optimun pH of 5.2. The apparent Km for H2O2 and KI is 0.16 . 10(-3) M and 1 . 10(-3) M, respectively.

Animals↗
PubMed1979

Characterization of an adenosine triphosphatase from myeloblasts infected with the avian myeloblastosis virus.

An adenosine triphosphatase (ATPase EC 3.6.1.3) was partially purified from myeloblasts of chicken infected with the avian myeloblastosis virus and some of its molecular, catalytic and immunological properties were compared with that of the ATPase purified from the virus. Both the enzymes possessed almost same electrophoretic mobility, molecular weight, S20,w value, substrate specificity, metal-ion requirement, apparent Km value and sensitivity to inhibitors and activator. Evidence also indicated immunological identity of the two enzymes. The insensitivity of this enzyme to rutamycin or ouabain and extreme sensitivity to most of the detergents, trypsin and mercurials are the remarkable properties of this enzyme.

Adenosine Triphosphatases↗
PubMed1979

Partial purification and characterization of the phosphate transporter from bovine heart mitochondria.

A highly active phosphate transporter was extracted with octylglucoside from bovine heart submitochondrial particles that were first partially depleted of other membrane components. It was then partially purified by ammonium sulfate fractionation. After reconstitution of the transporter into liposomes prepared with a crude mixture of soybean phospholipids, the Pi/OH exchange, but not the Pi/Pi exchange, was stimulated three- to fourfold by valinomycin and nigericin in the presence of K+. Both Pi/OH and Pi/Pi exchange activities were sensitive to mercurials and other SH reagents. The rutamycin-sensitive ATPase complex from mitochondria was reconstituted together with the phosphate transporter and adenine nucleotide transporter into liposomes. After inhibition of externally located ATPase, the hydrolysis of ATP was sensitive to atractyloside and mersalyl.

Adenosine Triphosphatases↗
PubMed1978

Viral adenosine triphosphatase.

The catalytic and immunological properties of an adenosine triphosphatase from different types of virus have been studied. The avian myeloblastosis virus has been found to be specialized in holding this enzyme in a highly active state as compared to other virus with respect to their host cell enzyme. Catalytically myeloblastosis virus and Rous virus ATPase behave alike, while that of the Reo virus is significantly different.

Adenosine Triphosphatases↗