[Characteristics of functioning of succinate dehydrogenase from flight muscles of the bumblebee Bombus terrestris (L.)].

It was found that the succinate oxidation rate in mitochondria of flight muscles of Bombus terrestris L. in- creased by a factor of 2.15 after flying for 1 h. An electrophoretically homogenous preparation of succinate dehydrogenase with a specific activity of 7.14 U/mg protein and 81.55-fold purity was isolated from B. terrestris flight muscles. It is shown that this enzyme is represented in the muscle tissue by only one isoform with R,f = 0.24. The molecular weight of the native molecule and its subunits A and B was determined. The kinetic characteristics ofsuccinate dehydrogenase (Km = 0.33 mM) and the optimal concentration of hydrogen ions (pH 7.8) were established, and the effect of salts on the enzyme activity was studied. The role of succinate as a respiratory substrate in stress and the structural and functional characteristics of the succinate dehydrogenase system in the flight muscles of insects are discussed.

[Molecular and biochemical studies of succinate dehydrogenase in rat liver under conditions of alloxan diabetes]. / Molekuliarnye i biokhimicheskie issledovaniia suktsinatdegidrogenazy v pecheni krys v usloviiakh alloksanovogo diabeta.

Experimental alloxan diabetes in rats causes an increase in the activity of liver succinate dehydrogenase (SDH) without changes in its isozyme composition. The observed increase in the catalytic activity of SDH clearly correlates with the intensification of transcription of the genes encoding catalytic dimer of SDH. Analysis of the methyl status of the promoters of the genes, encoding the catalytic dimer of SDH in rats under normal and experimental conditions did not reveal any dependence on the level of their expression. The obtained results of bisulfite sequencing indicate a passive role of the epigenetic mechanism of regulation of SDH gene expression in the development of alloxan diabetes. The transcription factor CREB, responsible for of gluconeogenesis in diabetes, may play an important role in the control of the transcriptional activity of the sdha and sdhb genes.

[Role of differential expression of sdh1-1 and sdh1-2 genes in alteration of isoenzyme composition of succinate dehydrogenase in germinating maize seeds].

A probable mechanism of alteration of the isoenzyme composition of succinate dehydrogenase (SDH) due to differential expression of genes encoding subunit A was considered. The alteration of SDH activity during maize seed germination was investigated, and its maximal activity on day 4-5 of germination was found. The alteration of the sdh1-1 and sdh1-2 gene expression level during maize seed germination was evaluated using the quantitative polymerase chain reaction method. The presence of four forms of the studied enzymes, providing multiple SDH functions was found in maize inflorescence using electrophoresis in polyacrylamide gel.

Physicochemical and kinetic characteristics of isoforms of isocitrate lyase from corn.

Three electrophoretically homogeneous isocitrate lyase (ICL) isoforms were obtained by 4-step purification from corn scutellum (ICL(1) and ICL(2)) and green leaves (ICL). Their physicochemical, kinetic, and regulatory properties were analyzed. The molecular masses of ICL(1), ICL(2) , and ICL isoforms determined by gel filtration are 164, 207, and 208 kDa, respectively. The proteins have homotetrameric quaternary structure with subunit molecular masses of 43, 48, and 47 kDa for ICL(1), ICL(2), and ICL, respectively. We found some differences in pH optimum, K(m), and regulation by divalent metal cations between ICL(1) and ICL(2) and significant similarity of ICL(2) and ICL. Based on these data, we suggest the participation of these isoforms in metabolic regulation of the glyoxylate cycle, organic acid metabolism during photorespiration in leaves and acidosis in corn seeds.

Features of structural organization and expression regulation of malate dehydrogenase isoforms from Rhodobacter sphaeroides strain 2R.

Two isoforms of malate dehydrogenase (MDH), dimeric and tetrameric, have been found in the purple non-sulfur bacterium Rhodobacter sphaeroides strain 2R, devoid of the glyoxylate shunt, which assimilate acetate via the citramalate cycle. Inhibitory analysis showed that the 74-kDa protein is involved in tricarboxylic acid cycle, while the 148-kDa MDH takes part in the citramalate pathway. A single gene encoding synthesis of the isologous subunits of the MDH isoforms was found during molecular-biological investigations. The appearance in the studied bacterium of the tetrameric MDH isoform during growth in the presence of acetate is probably due to the increased level of mdh gene expression, revealed by the real-time PCR, the product of which in cooperation with the citramalate cycle enzymes plays an important role in acetate assimilation.

[Role of transamination in the mobilization of respiratory substrates in germinating seeds of castor oil plants].

The metabolism of 1,4-14C-succinate and 2,3-14C-succinate and the activity of succinic semialdehyde dehydrogenase (EC 1.2.1.16) were studied in germinating seeds of castor oil plants (Ricinus communis L.). Succinate metabolism involved succinate dehydrogenase and was sensitive to metabolites of the gamma-aminobutyric acid shunt. Considerable accumulation of the label in amino acids reflected the progression of transamination reactions. Succinic semialdehyde dehydrogenase was purified from the endosperm of castor oil plants. Kinetic characteristics of the enzyme were evaluated. Our study indicates that the mobilization of respiratory substrates during germination of castor oil plants is related to active transamination of ketoacids in the Krebs cycle and involves the gamma-aminobutyric acid shunt.