ACTIVITY OF REGULATORY ENZYMES OF THE TCA CYCLE IN THE CELL
UNDER CONDITION OF DISORDER OF DIGESTIVE SYSTEM
L. G. Kalachnyuk
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National Universityof Life and Environmental Sciences of Ukraine,
Heroiv Oborony str., 15; Kyiv, 03041, Ukraine
It has been early discovered disturbance in the functioning of reactions of anaerobic-glycolytic pathway, especially at its final stage (during the formation of pyruvate and lactate) in hepatocytes of newborn calves under conditions of disorder of processes of digestion. The purpose of the following investigations was to continue the study of influence of factors of digestive system disorders of alimentary nature on intracellular metabolism, especially on activity of regulatory enzymes of the tricarboxylic acid (TCA) cycle in the liver of newborn calves.
For the research, 1–7 days old calves were used. Animals that are on the principle of unique (equivalent in age, breed, sex, weight) divided into two groups (n=5) with a body weight 28–36 kg. Calves of the first (I, control) group were clinically healthy, and the second (II, experimental) — a disorder of the digestive system of alimentary origin. The activity of citrate synthase (CS; EC 4.1.3.7) and cytochrome с oxidase (COX, EC 1.9.3.1) in the ultrasound-treated liver homogenates were determined by the generally accepted methods (ShepherdD., GarlandP.B., 1969; SmithL., ConradeH., 1956). It has been taken into account that the level of CS activity reflects the state of the initial phase of the TCA cycle functioning — more precisely, rate of condensation of acetyl-CoA with oxaloacetate. It reflects citric acid production efficiency and successfulness of subsequent series of important reactions. Additionally, the COX (and O2) is the ultimate supply of electrons coming from oxidation of nutrients, as well as direct transport of protons across the inner membrane of mitochondria. This in complex provides the ultimate effect of stage biological oxidation, ie recovery of molecular oxygen by electrons.
As a result, the research found that, under conditions of disorder of the digestive system of alimentary nature in hepatic cells of newborn calves, the activity of CS is significantly decreased. CS catalyzes the initial stage of the TCA cycle functioning and hence the rate and capacity of catabolism and synthesis of many important intermediates in it.
Disorders of the digestive processes also significantly reduces the activity of COX, ie, inhibits the final stage of oxidation-reduction of molecular oxygen by electrons. It should be noted that a direct reflection of the regularities of the detected changes can be considered as the value of the СОХ : CS ratio. The revealed changes are associated with disorders of structural and functional state of mitochondrial membranes and other compartment of hepatic cells due to deficiency of nutrients supplies from the gastrointestinal tract and inhibition of many important parts of the overall and intracellular metabolism.
Keywords:ENZYMES OF THE TCA CYCLE, CITRATE SYNTHASE, CYTOCHROM-C-OXIDASE, HEPATIC CELLS, SYSTEM OF DIGESTION, NEWBORNCALVES
