Biomedical subjects

A P Pleten'

Publications and source records attributed to A P Pleten'.

5 recordsLinked to original sources

PubMed2003

Ascorbate-induced oxidation of glyceraldehyde-3-phosphate dehydrogenase.

Oxidation of the essential cysteins of glyceraldehyde-3-phosphate dehydrogenase into the sulfenic acid derivatives was observed in the presence of ascorbate, resulting in a decrease in the dehydrogenase activity and the appearance of the acylphosphatase activity. The oxidation was promoted by EDTA, NAD(+), and phosphate, and blocked in the presence of deferoxamine. The ascorbate-induced oxidation was suppressed in the presence of catalase, suggesting the accumulation of hydrogen peroxide in the conditions employed. The data indicate the metal-mediated mechanism of the oxidation due to the presence of metal traces in the reaction medium. Physiological importance of the mildly oxidized GAPDH is discussed in terms of its ability to uncouple glycolysis and to decrease the ATP level in the cell.

Animals↗

PubMed2003

Acceleration of glycolysis in the presence of the non-phosphorylating and the oxidized phosphorylating glyceraldehyde-3-phosphate dehydrogenases.

Mild oxidation of glyceraldehyde-3-phosphate dehydrogenase in the presence of hydrogen peroxide leads to oxidation of some of the active site cysteine residues to sulfenic acid derivatives, resulting in the induction of acylphosphatase activity. The reduced active sites of the enzyme retain the ability to oxidize glyceraldehyde-3-phosphate yielding 1,3-diphosphoglycerate, while the oxidized active sites catalyze irreversible cleavage of 1,3-diphosphoglycerate. It was assumed that the oxidation of glyceraldehyde-3-phosphate dehydrogenase by different physiological oxidants must accelerate glycolysis due to uncoupling of the reactions of oxidation and phosphorylation. It was shown that the addition of hydrogen peroxide to the mixture of glycolytic enzymes or to the muscle extract increased production of lactate, decreasing the yield of ATP. A similar effect was observed in the presence of non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase catalyzing irreversible oxidation of glyceraldehyde-3-phosphate into 3-phosphoglycerate. A role of glyceraldehyde-3-phosphate dehydrogenase in regulation of glycolysis is discussed.

Adenosine Triphosphate↗

PubMedDate not supplied

[The non-functioning chaperonin GroEL stimulates protein aggregation].

To clarify the role of chaperones in the development of amyloid diseases, the interaction of the chaperonin GroEL with misfolded proteins and recombinant prions has been studied. The efficiency of the chaperonin-assisted folding of denatured glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was shown to decrease in the presence of prions. Prions are capable of binding to GroEL immobilized on Sepharose, but this does not prevent the interaction between GroEL and other denatured proteins. The sizes of individual proteins (GroEL, GAPDH, and the recombinant prion), as well as aggregates formed after their mixing, were determined by the dynamic light scattering method. It was shown that at 25 degrees C the non-functioning chaperonin (equimolar mixture of GroEL and GroES in the absence of Mg-ATP) bound prion yielding large aggregates (greater than 400 nm). The addition of Mg-ATP decreased significantly the aggregate size to 70-80 nm. On the blocking of one of the chaperonin centers by oxidized denatured GAPDH, the aggregate size increased to 1200 nm, and the addition of Mg-ATP did not prevent the aggregation. These data indicate the significant role of chaperonins in the formation of amyloid structures and demonstrate the acceleration of aggregation in the presence of functionally inactive chaperonins. The suggested model can be used for the analysis of the efficiency of antiaggregants in the system containing chaperonins.

Amyloid↗

PubMedDate not supplied

[Isolation of renin from human kidneys].

Isolation and partial purification of renin from human kidney was carried out as follows: defatting of the homogenized kidney; extraction with methyl cellosolve; chromatography on DEAE cellulose; affinity chromatography using immobilized pepstain. Activity of the preparation obtained was 0.1 GU/mg of protein. The preparation of human renin might be used for measurement of renin activity in blood of patients.

Angiotensinogen↗

PubMedDate not supplied

[Isolation and purification of angiotensinogen from swine and sheep plasma].

Angiotensinogen (a substrate of renin) was isolated from pig and sheep blood plasma. Content of angiotensinogen was estimated in the preparations obtained by an indirect biological method, which was based on estimation of an increase in blood pressure in rats, caused by angiotensin, liberated from angiotensinogen during incubation with renin. The preparation, obtained by ammonium sulphate fractionation of pig blood plasma, contained 0.4% of angiotensinogen. Angiotensinogen was also isolated from sheep blood plasma using ammonium sulphate fractionation, DEAE-Sephadex chromatography and gel filtration through Sephadex G-100; this preparation contained 10-13% of angiotensinogen.

Angiotensinogen↗