Rubens Rosa

Blood constituents and electrophoretic patterns in antarctic birds: Penguins and skuas

Abstract 1. 1. A survey has been carried out on the blood constituents of penguins from the Pygoscellidae family, Pygoscellis antartica , P. papua and P. adeliae , and of skuas ( Chataracta maccormicki ). 2. 2. Glucose, non-protein nitrogen compounds, proteins, lipids and inorganic compounds and the electrophoretic patterns for hemoglobin, serum proteins and lipoproteins were studied. 3. 3. The values obtained for glucose partition in the blood, glycosylated hemoglobin and non-protein nitrogen compounds, are discussed.

The profile of the glycolytic system and the metabolic activity of chicken erythrocytes

1. 1. The metabolic activity and the glycolytic system from chicken erythrocytes were studied in the present paper. Intact chicken red blood cells hardly show any measurable glucose utilization and fail to produce lactic acid. 2. 2. Chicken erythrocytes possess the whole set of glycolytic enzymes (HK, PGI, PFK, FruP2-Ald, GAPDH, PGK, ENO, PK, LDH). 3. 3. The incubation of hemolysates with hexose-phosphates (G-6-P, F-6-P, F-1-P, FruP2) does not enhance the formation of lactic acid. However, in the presence of triosephosphates (2,3-DiPGA, 3-PGA, 2-PGA) there is a net production of lactic acid in the reaction system, mainly when 2,3-DiPGA is the metabolite used.

Activities of some glycolytic enzymes in the major salivary glands of some laboratory animals

Abstract 1. 1. Hexokinase, aldolase, pyruvate kinase and lactic dehydrogenase activities were determined in the major salivary glands of hamsters, mice, guinea pigs and rats. 2. 2. Significant species differences in the specific activity of the enzymes studied were observed.

Kinetic properties of pyruvate kinase from the epaxial muscle of the marine fishes Mugil lisa and Chaetoditerus faber

Kinetic studies were carried out on the reaction catalyzed by pyruvate kinase (ATP:pyruvate phosphotransferase, E.C. 2.7.1.40) purified from white striated (epaxial) muscle of two marine fish Mugil lisa (Brazilian mullet) and Chaetoditerus faber (harvest fish). This included the establishment of kinetic parameters. Attention was given to the effect of fructose 1,6-bisphosphate (Fru-P2) on PK activity. Effects of ATP, alanine and the divalent ions, Mg2+, Mn2+, Cu2+, Be2+ and Co2+, on the fish muscle enzyme were also studied.

Metabolism in vitro of the submandibular salivary gland from rats subjected to various nutritional conditions.

Abstract Rats were subjected to various nutritional conditions and the ability of slices of their submandibular salivary glands to produce lactic acid and to consume endogenous glycogen was examined under aerobic and anaerobic conditions. Oxygen uptake tended to increase during 60 min of incubation in the absence of added substrate. The endogenous glycogen content decreased progressively during fasting. When incubated in a substrate-free medium, glycogen from the slices was consumed within the first 15 min. Except for one group fasted for 24 hr, lactic acid after each incubation decreased but only to a statistically significant extent after 60 min of incubation

COMPARATIVE LEVELS BETWEEN ENZYMES OF THE GLYCOLYTIC PATHWAY FROM ERYTHROCYTES AND SOMATIC TISSUES OF THE CHICKEN GALLUS-GALLUS DOMESTICUS

A comparative study on the glycolytic enzymes from chicken erythrocytes and somatic tissues has been carried out, the results being shown as active units per mg protein in supernatants of 1085, 12,100 and 106,000 g fractionated centrifugation. The profiles of the glycolytic enzymes have been analyzed in terms of their activity relative to hexokinase and as the ratios between pairs of enzymes bearing a product-substrate relationship. Chicken erythrocyte displays a very peculiar profile of glycolytic enzymes. It possesses a FruP2-activated pyruvate kinase of the L isoenzyme type, which does not seem to be the predominant isoenzyme together with the M type, the content in glycolytic enzymes being much lower than in the somatic tissues.

Purification and properties of pyruvate kinase from the striated muscle of the ice-fish Chaenocephalus aceratus Loenberg

Abstract 1. 1. Pyruvate kinase from the striated muscle of Chaenocephalus aceratus was purified to homogeneity by a 3-step process, 1 step involving ammonium sulfate precipitation and 2 steps with phosphocellulose and KC1 and phosphoenolpyruvate elution. The final specific activity of the enzyme was 188.8 UI/mg and the overall yield 20%. The apparent molecular weights of the native enzyme suggests that the protein is present as a homotetramer. 2. 2. The cellulose acetate electrophoresis showed the presence of only 1 isoenzymatic form with electrophoretic mobility similar to that of the L type PK from rat liver. 3. 3. The enzyme possesses an optimal pH around 6.5 and an energy of activation of 15,000 cal/mol. Among 6 different buffers used, imidazole-HCl was the only one which did not interfere with the enzyme activity. Furthermore, this buffer showed to be the most efficient one in stabilizing the PK at 40°C for 30 min.

Purification and properties of buffalo (Bubalus bubalis) erythrocyte hexokinase

Buffalo erythrocytes contain one isozyme of hexokinase that apparently lacks microheterogeneity as shown by chromatographic properties. A single protein band was detected by means of Western blotting using an antibody raised in rabbits against homogeneous rat brain hexokinase I. The native protein has a molecular weight of 200,000 +/- 2880 by gel filtration. Partial purification of erythrocyte hexokinase by a combination of several procedures, including affinity chromatography, which was previously applied successfully to the purification of other mammalian type I hexokinases, produced a partially purified enzyme that showed several contaminants after SDS-polyacrylamide gel electrophoresis. The affinity of buffalo erythrocyte hexokinase for glucose (K(m) = 0.012 +/- 0.001 mM) is lower than most other mammal hexokinases type I. It phosphorylates other sugars, with considerably higher K(m) values. This isozyme is able to use MgATP but does not use MgGTP, MgCTP or MgUTP. We used inhibition patterns, obtained with products to elucidate enzyme sequential mechanisms. Our results are clearly in agreement with a random sequential mechanism and in disagreement with an ordered sequential mechanism with either glucose or ATP as the obligatory first substrates. The ADP inhibition was of mixed type with both ATP and glucose as substrates.

Glucose metabolism in the erythrocytes of the buffalo (Bubalus bubalis).

14CO2 production from [1-14C] glucose, the rate of glycolysis measured by the value of lactate production and the activities of various enzymes were determined in buffalo erythrocytes. Buffalo red cell glycolytic metabolites were estimated and used for the calculation of the mass action ratios of reactions catalyzed by the glycolytic enzymes of Bubalus bubalis. A comparison of the values of the mass action ratios with the equilibrium constants of the various glycolytic reactions indicate that hexokinase, phosphofructokinase, phosphoglycerate kinase and pyruvate kinase reactions are displaced from equilibrium, suggesting a regulatory role for each of these enzymes in buffalo erythrocyte glycolysis.

Metabolic activity of the sticker's lymphosarcoma

Some parameters (glycolysis, respiration, levels of glycolytic enzymes) of the lymphoid cells from the Stickers lymphosarcoma were established in order to better define the biochemical behavior of the venereal tumor of the dog. For comparative purposes lymphocytes from peripheral blood of normal and tumor-bearing dogs were also studied. Lactic acid produced by the tumor cells during aerobic glycolysis is liberated in the reaction medium. Oxygen uptake is enhanced in the presence of succinate, but not with pyruvate, alpha-ketoglutarate, or malate as substrates. Higher levels of some of the enzymes from the glycolytic pathways as well as differences on the physicochemical and kinetic properties of the glycolytic regulatory enzymes are found in Stickers tumor cells, when compared with the lymphocytes from peripheral blood of normal and tumor-bearing dogs. A fructose-bisphosphate positively modulated pyruvatekinase is found in the tumor cells.