Metry Bacila

On the nucleotide binding domain of fructose-1,6-bisphosphatase☆

Abstract Native chicken liver fructose-1,6-bisphosphatase (Fru-P2ase) can bind to blue dextranSepharose affinity column and is not displaced by its sugar-phosphate substrate; however; it is readily eluted by the inhibitor 5′-AMP. Treatment of Fru-P2ase with pyridoxal 5′-phosphate (pyridoxal-P) in the presence of the substrate, fructose 1,6-bisphosphate, followed by reduction with NaBH4 leads to the formation of active pyridoxal-P derivatives of the enzyme showing diminished sensitivity to AMP inhibitor. The modified enzyme does not bind to the affinity column. On the other hand, in the presence of AMP modification of Fru-P2ase with pyridoxal-P occurs at the catalytic site; this modification does not alter its binding behavior toward the dye ligand. Blue dextran can also protect Fru-P2ase against AMP inhibition, and it is a competitive desensitizer for the nucleotide ligand. The results establish that blue dextran binds specifically to the allosteric site of the enzyme, and that the structure of this site may resemble that of the dinucleotide fold in other enzymes. Like native Fru-P2ase, digestion of pyridoxal-P-Fru-P2ase (with regulatory properties altered) with subtilisin causes a severalfold increase in the catalytic activity measured at pH 9.2, without significant change in the activity at pH 7.5, and produces a peptide with 56 amino acids. The residual subunit, Mr ~ 30,000, was found to contain all of the incorporated pyridoxal-P.

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.

Improving the efficiency of alcohol production with respiration-deficient yeast mutants

Abstract Respiration-deficient yeast mutants have been used in experiments aimed at improving the efficiency of ethanol production in the alcoholic fermentation of sugar-cane juice.

Purification and properties of a polyphenoloxidase from the fresh water snail Biomphalaria glabrata

Abstract 1. 1. A polyphenoloxidase (ortho-diphenol:O 2 -oxido-reductase, E.C. 1.10.3.1) has been partially purified from Biomphalaria glabrata . 2. 2. It is an enzyme with low substrate specificity, being active with di-hydroxy and triphenols, as well as with a variety of aromatic amines. The side chain structure of the latter compounds seems to directly influence enzyme activity. 3. 3. The effect of several cations as Cu 2+ substituents in the activation of the enzyme were studied, vanadium (V 3+ ) showing higher activity than Cu 2+ .

N-acylsarcosines as inhibitors of respiration and glycolysis and glycolytic enzymes☆

Abstract Sodium- N -lauroyl sarcosinate and sodium- N -palmitoyl sarcosinate inhibit the respiration and anaerobic glycolysis of isolated mouse diaphragm. Rabbit heart glucokinase and rabbit muscle fructose-1,6-diphosphate aldolase are also inhibited by SLS and SPS, which appear to act as denaturing agents. In concentrations ranging from 1 × 10 −2 m to 3 × 10 −2 m for SLS and 2.5 × 10 −5 m to 2.5 × 10 −4 m for SPS both compounds cause progressive unfolding of rabbit muscle aldolase, as evidenced by the exposure of all the buried sulfhydryl groups; this process is associated with loss of enzymatic activity.

THE EFFECT OF CERTAIN PHENOTHIAZINES ON THE STRUCTURE AND METABOLIC ACTIVITY OF SARCOSOMES OF GUINEA PIG HEART.

Abstract The metabolic effects of phenothiazine derivatives have been attributed to the inhibition of several of the most fundamental properties of the mitochondria. Enzymes not linked to the mitochondrial activity were also reported as being inhibited by phenothiazine compounds. However, most of the effects on isolated mitochondria should be considered a consequence of their action on the mitochondria itself. The effects of several phenothiazine compounds on the normal properties of mitochondria were then studied by polarographic determinations; their effect on the fine structure of these subcellular particles was studied by turbidimetry and by electronmicroscopy.

Correlation of inhibition of fructose 1,6-bisphosphatase by AMP and the presence of the nucleotide-binding domain

Abstract Chicken liver fructose 1,6-bisphosphatase binds to blue dextran-Sepharose affinity columns and is eluted by AMP, an allosteric inhibitor of the enzyme. On the other hand, bumblebee fructose 1,6-bisphosphatase, which is not inhibited by AMP, does not bind to blue dextran-Sepharose. Chicken liver 1,6-bisphosphatase binds 3.6 mol of AMP/mol of enzyme, while the bumblebee enzyme binds no AMP. However, bumblebee fructose 1,6-bisphosphatase can be activated by subtilisin, indicating that it possesses a protease-sensitive region similar to that present in mammalian fructose 1,6-bisphosphatase.

Multiple forms of phosphofructokinase in developing rabbit and guinea pig tissues.

Abstract Multiple forms of phosphofructokinase in striated muscle and cardiac muscle of developing rabbit ( Oryctolagus cuniculus ) undergo changes with development, but not in brain and liver. The cardiac muscle of the 1-day-old rabbit contains phosphofructokinase A 4 together with the four hybrid forms which were tentatively called A 3 C, A 2 C 2 , AC 3 , and C 4 . In older animals, phosphofructokinase C 4 disappears first, followed by the hybrid forms, and only phosphofructokinase A 4 persists in the adult animal. Both phosphofructokinase A 4 and phosphofructokinase C 4 , as well as their hybrid forms, are present in developing embryonic brain and also in the brains of adult animals. Developing rabbit liver contains a single form of phosphofructokinase, but two isoenzymes are consistently seen in guinea pig liver. In striated muscle from fetal and 1-day-old rabbit, two isoenzymes are found, tentatively identified as A 4 and the A 3 C hybrid. The results suggest that fetal phosphofructokinase A 4 and phosphofructokinase C 4 , and their hybrids, might be present in striated muscle. Guinea pig tissues show a pattern of phosphofructokinase isoenzymes different from that in rabbit tissues.

Interference of phenothiazine compounds in the colorimetric determination of inorganic phosphate.

Abstract It has been shown that phenothiazine derivatives interfere with the colorimetric determination of inorganic phosphate by methods in which phosphomolybdic acid is one of the reaction components. Furthermore, it has been shown that PTZ derivatives form a complex with phosphomolybdic acid which can be detected by infrared spectrophotometry. Such finding indicates that, in experiments trying to show the effect of phenothiazine derivatives on enzymes in which the assay of inorganic phosphate is the parameter used in order to define the enzymic effect, it is necessary to plan the experiment carefully.