Relationship of the hexose monophosphate shunt to the endogenous metabolism of cell-free extracts of Mycobacterium phlei

Sutton, W. B. (The Lilly Research Laboratories, Indianapolis, Ind.). Relationship of the hexose monophosphate shunt to the endogenous metabolism of cell-free extracts of Mycobacterium phlei. J. Bacteriol. 85:476-484. 1963.-The endogenous reduction of 2,6-dichlorophenol-indophenol (DPIP) by cell-free extracts of Mycobacterium phlei has been linked to the presence of glucose-6-phosphate (G-6-P) dehydrogenase functioning in connection with a reduced triphosphopyridine nucleotide (TPN)-DPIP reductase. The necessary substrate and coenzyme, i.e., G-6-P and TPN, are contained in the cell-free bacterial extract. The only required addition to activate the system is a suitable electron acceptor. The accumulation of G-6-P and the presence of 6-phosphogluconic dehydrogenase in the cell-free extract suggest that the hexose monophosphate shunt mechanism is impaired by sonic treatment of M. phlei.

Structure of a phosphorylated polysaccharide from Shewanella putrefaciens strain S29

A phosphorylated polysaccharide was isolated from the aqueous layer of the phenol-water extract of a non-halophilic bacterium Shewanella putrefaciens strain S29. The glycosyl phosphate linkage in the polysaccharide was split under mild acid conditions to give, after borohydride reduction, a phosphorylated oligosaccharide-alditol. On the basis of sugar analysis and 1H, 13C and 31P NMR spectroscopy, including 2D COSY, relayed COSY, rotating-frame NOE spectroscopy (ROESY), heteronuclear 13C,1H COSY, and H-detected heteronuclear 1H,31P multiple-quantum coherence (HMQC), it was concluded that the polysaccharide is built up of tetrasaccharide-phosphate repeating units having the following structure: [sequence: see text] where QuiNAc and Qui4NAc are 2-acetamido-2,6-dideoxyglucose and 4-acetamido-4,6-dideoxyglucose, respectively.

BRAIN MITOCHONDRIA. II. THE RELATIONSHIP OF BRAIN MITOCHONDRIA TO GLYCOLYSIS

A mitochondrial fraction prepared from calf brain cortex possessed negligible glycolytic activity in the absence of the enzymes of the high speed supernatant fraction. When mitochondria were added to a supernatant system supplemented with optimal amounts of crystalline hexokinase, a 20 per cent stimulation of glycolysis was observed. The supernatant fraction produced minimal amounts of lactate in the absence of exogenous hexokinase; the addition of mitochondria doubled the lactate production. The substitution of glycolytic intermediates for glucose as substrates as well as the addition of exogenous glycolytic enzymes to the supernatant fraction or supernatant fraction plus mitochondria indicated that the mitochondria contributed mainly hexokinase and phosphofructokinase. By direct assay of all of the enzymes of the glycolytic pathway, only hexokinase and phosphofructokinase were shown to be concentrated in the mitochondrial fraction. All other glycolytic enzymes were found to exhibit higher total and specific activities in the supernatant fraction.

STUDIES ON THE MODE OF ACTION OF DIPHTHERIA TOXIN. I. PHOSPHORYLATED INTERMEDIATES IN NORMAL AND INTOXICATED HELA CELLS

Intracellular levels of ATP, GTP, and hexose phosphates have been determined in HeLa cells at intervals after exposure to saturating doses of diphtheria toxin. Toxin causes no significant change in the level of any of these phosphorylated intermediates either in the presence or absence of glucose over a period of at least 5 to 6 hours. It is concluded that the inhibition of protein synthesis which occurs in HeLa cells at about 2 hours after the addition of saturating doses of toxin, does not result from an effect of toxin on energy metabolism.

SEPARATION OF TEICHOIC ACID OF STAPHYLOCOCCUS AUREUS INTO TWO IMMUNOLOGICALLY DISTINCT SPECIFIC POLYSACCHARIDES WITH ALPHA- AND BETA-N-ACETYLGLUCOSAMINYL LINKAGES RESPECTIVELY. ANTIGENICITY OF THEICHOIC ACIDS IN MAN

Human sera were found to contain antibodies precipitating with each of two samples of teichoic acid of Staphylococcus aureus prior to immunization; these antibodies were probably formed as a result of contact or infection with this microorganism. Injection of teichoic acid into two individuals resulted in a rise in circulating antibody to teichoic acid; a third subject probably had a primary response to α-teichoic acid. Quantitative precipitin and agar diffusion studies revealed the presence of two distinct antibodies in the sera and showed that each specimen of teichoic acid was a mixture of two polymers an α-linked N-acetylglucosaminyl-ribitol polymer and a β-linked N-acetylglucosaminyl-ribitol polymer, termed α- and β-teichoic acids respectively. The α-teichoic acid anti-α-teichoic acid system was inhibited best by α-linked glucosaminides and the β-anti-β-teichoic acid system was inhibited best by a β-linked glucosaminide. The α- and (β-teichoic acids could be separated from each other by specific precipitation under appropriate conditions and recovered from the washed specific precipitates. The existence of two distinct teichoic acid polymers raises important questions as to cell wall structure and the biosynthesis of the teichoic acids.

SOME PROPERTIES OF FRUCTOSE 1,6-DIPHOSPHATASE OF RAT LIVER AND THEIR RELATION TO THE CONTROL OF GLUCONEOGENESIS

1. Fructose 1,6-diphosphatase has been purified tenfold from rat liver. The final preparation was not contaminated by either glucose 6-phosphatase or phosphofructokinase. The properties of the enzyme have been investigated in an attempt to define factors that could be of revelance to metabolic control of fructose 1,6-diphosphatase activity. 2. The metal ions Fe(2+), Fe(3+) and Zn(2+) inhibited the activity of fructose 1,6-diphosphatase even in the presence of an excess of mercaptoethanol; other metal ions tested had no effect. The inhibition produced by Zn(2+) was reversed by EDTA, but that produced by either Fe(2+) or Fe(3+) was not reversible. 4. The enzyme has a very low K(m) for fructose 1,6-diphosphate (2.0mum). Concentrations of fructose 1,6-diphosphate above 75mum inhibited the activity; however, even at very high fructose 1,6-diphosphate concentrations only 70% inhibition was obtained. 5. The activity was also inhibited by low concentrations of AMP, which lowered V(max.) and increased K(m) for fructose 1,6-diphosphate. Evidence is presented that suggests that AMP can be defined as an allosteric inhibitor of fructose 1,6-diphosphatase. 6. The inhibitions by both fructose 1,6-diphosphate and AMP were extremely specific. Also, the degree of inhibition was not affected by the presence of intermediates of glycolysis, of the tricarboxylic acid cycle, of amino acid metabolism or of fatty acid metabolism. 7. It is suggested that the intracellular concentrations of AMP and fructose 1,6-diphosphate could be of significance in controlling the activity of fructose 1,6-diphosphatase in the liver cell. The possible relationship between these intermediates and the control of gluconeogenesis is discussed.

PROPERTIES OF PHOSPHOFRUCTOKINASE FROM RAT LIVER AND THEIR RELATION TO THE CONTROL OF GLYCOLYSIS AND GLUCONEOGENESIS

1. Phosphofructokinase from rat liver has been partially purified by ammonium sulphate precipitation so as to remove enzymes that interfere in one assay for phosphofructokinase. The properties of this enzyme were found to be similar to those of the same enzyme from other tissues (e.g. cardiac muscle, skeletal muscle and brain) that were previously investigated by other workers. 2. Low concentrations of ATP inhibited phosphofructokinase activity by decreasing the affinity of the enzyme for the other substrate, fructose 6-phosphate. Citrate, and other intermediates of the tricarboxylic acid cycle, also inhibited the activity of phosphofructokinase. 3. This inhibition was relieved by either AMP or fructose 1,6-diphosphate; however, higher concentrations of ATP decreased and finally removed the effect of these activators. 4. Ammonium sulphate protected the enzyme from inactivation, and increased the activity by relieving the inhibition due to ATP. The latter effect was similar to that of AMP. 5. Phosphofructokinase was found in the same cellular compartment as fructose 1,6-diphosphatase, namely the soluble cytoplasm. 6. The properties of phosphofructokinase and fructose 1,6-diphosphatase are compared and a theory is proposed that affords dual control of both enzymes in the liver. The relation of this to the control of glycolysis and gluconeogenesis is discussed.

CARP MYOGENS OF WHITE AND RED MUSCLES. GROSS ISOLATION ON SEPHADEX COLUMNS OF THE LOW-MOLECULAR-WEIGHT COMPONENTS AND EXAMINATION OF THEIR PARTICIPATION IN ANAEROBIC GLYCOGENOLYSIS

1. The combined low-molecular-weight protein components of the myogens from carp white and red muscles [about 30% (w/w) of the myogen proteins] have been isolated by gel filtration on Sephadex G-75 columns. 2. The presence in this fraction from myogen of white muscle of the three main electrophoretic components previously isolated has been confirmed, and the low molecular weight of the fourth component has been definitely established. 3. The exclusive presence of this fourth component in the myogen of red muscle, apart from myoglobin, has also been demonstrated. 4. Glycogenolysis experiments in vitro have shown that the low-molecular-weight protein fraction from carp myogen does not contain enzymes from the Embden-Meyerhof chain.

PATTERNS OF DIETARY AND HORMONAL INDUCTION OF CERTAIN NADP-LINKED LIVER ENZYMES

Estrogen and thyroxine induction of hepatic hexosemonophosphate shunt and NADP-linked malic dehydrogenases was studied in rats on chow and on a high-fat, low-carbohydrate diet. A different enzyme pattern resulted from treatment with each of the hormones; i.e., estrogen produced a greater effect on the dehydrogenases of the pentose phosphate pathway while thyroxine showed a greater influence on the malic enzyme. Both enzymes were inducible in animals adapted to a high-fat diet, suggesting that accelerated glucose absorption from the gastrointestinal tract is not an essential feature of the mechanism of hormonal induction. However, in the case of the shunt enzymes, availability of dietary carbohydrate resulted in greater increases in enzyme activity than did induction on a high-fat diet. Refeeding a high-carbohydrate diet after a 48-hr fast resulted in a simultaneous increase in both shunt dehydrogenases and malic enzyme, a fact which disproves the hypothesis that the adaptive increase of the former is secondary to a primary increase in the latter.

EVIDENCE FOR EXTRACELLULAR ENZYMIC ACTIVITY OF THE ISOLATED PERFUSED RAT HEART

1. The dissimilation of a number of externally added hexose phosphates and 5'-nucleotides by the perfused rat heart is described, and non-specific esterase and 5'-nucleotidase activity associated with the superficial cell membrane or vascular system has been demonstrated. 2. The rate of production of (14)CO(2) from [U-(14)C]glucose 6-phosphate suggests that oxidation occurred after hydrolysis to glucose. The incorporation of isotope from [U-(14)C]glucose 6-phosphate into glycogen was small, and similar to that obtained with [U-(14)C]glucose as substrate. 3. Glucose 6-phosphate was also partially isomerized to fructose 6-phosphate. Similarly, fructose 6-phosphate was converted mainly into glucose 6-phosphate, but also into glucose and inorganic phosphate. When fructose 1,6-diphosphate was added to the perfusate, a mixture of glucose 6-phosphate, fructose 6-phosphate and triose phosphates accumulated in the medium approximately in the equilibrium proportions of the phosphohexose-isomerase and triose phosphate-isomerase reactions, together with inorganic phosphate and some glucose. Glucose 1-phosphate was hydrolysed to glucose, but was not converted into glucose 6-phosphate. Leakage of enzymes out into the perfusion fluid did not occur. 4. This demonstration that phosphohexose isomerase, triose phosphate isomerase and aldolase may react with extracellular substrates at an appreciable rate suggests that these enzymes are attached to the cell membrane.

FRUCTOSE-1,6-DIPHOSPHATE REQUIREMENT OF STREPTOCOCCAL LACTIC DEHYDROGENASES

The lactic dehydrogenase of a strain of Streptococcus bovis specifically requires fructose-1,6-diphosphate for activity. Phosphate or fructose-1-6-diphosphate prevents inactivation of the dehydrogenase, but phosphate and other compounds cannot be substituted for the fructose-1,6-diphosphate required for activity. Lactic dehydrogenases of other species of Streptococcus show a similar requirement for fructose-1,6-diphosphate.

SYNTHESIS AND BREAKDOWN OF THE POLYPHOSPHATE FRACTION AND ACID PHOSPHOMONOESTERASE OF SACCHAROMYCES MELLIS AND THEIR LOCATIONS IN THE CELL

Weimberg, Ralph (Northern Regional Research Laboratory, Peoria, Ill.), and William L. Orton. Synthesis and breakdown of the polyphosphate fraction and acid phosphomonoesterase of Saccharomyces mellis and their locations in the cell. J. Bacteriol. 89:740-747. 1965.-The conditions for accumulation of polyphosphate in cells of Saccharomyces mellis differ in several respects from those for acid phosphomonoesterase biosynthesis and maintenance. Polyphosphate can be synthesized or degraded in vivo by resting cells, provided an energy source is present. Experiments with growing cells indicate that the enzyme systems involved in the metabolism of the polyphosphate fraction are constitutive, since cells respond immediately to changes in the level of inorganic phosphate in the external medium. There is no change in the acid phosphatase level in either resting cells or in cells in the lag phase of growth. Enzyme formation or breakdown occurs only in cells that are exponentially dividing. Enzyme is lost rapidly from derepressed cells when they are transferred to a phosphate-rich medium, falling to a very low value by the time the cell mass had doubled. Protoplasts of repressed cells were prepared to determine the location of ortho- and polyphosphates in the cell. Previous studies have shown that phosphomonoesterase is released as a soluble enzyme when derepressed cells become protoplasts. Unlike phosphomonoesterase in derepressed cells, the two phosphate fractions in repressed cells are still attached to the protoplast after the cell wall has been digested and are eluted only when the protoplast structure is lysed in cold water. However, it is also possible to extract a part of the two phosphate fractions from intact cells in the absence of snail gut extract by osmotic shock if the cells are first suspended in a solution of high salt concentration. This treatment with salt does not affect viability. These results do not permit a definite conclusion concerning the location of ortho- and polyphosphates in the cell, other than that they are associated with the protoplast and thus occupy a position different from that of the phosphomonoesterase.

MICROBIAL GROWTH ON C1 COMPOUNDS. SYNTHESIS OF CELL CONSTITUENTS BY METHANE- AND METHANOL-GROWN PSEUDOMONAS METHANICA

1. A study has been made of the incorporation of carbon from [(14)C]methane, [(14)C]methanol and [(14)C]bicarbonate by cultures of Pseudomonas methanica growing on methane, and [(14)C]methanol by cultures of the same organism growing on methanol. 2. The distribution of radioactivity within the non-volatile constituents of the ethanol-soluble fractions of the cells, after incubation with labelled compound for periods up to 3min., has been analysed by chromatography and radioautography. 3. Over 90% of the radioactivity fixed from [(14)C]methane or [(14)C]methanol at the earliest times of sampling appeared in phosphorylated compounds. Glucose phosphate and fructose phosphate together constituted the largest part of the radioactive phosphates (70-90%); phosphoglycerate was a relatively minor component (2-17%). Other compounds becoming labelled during the incubation included glycine, serine, glutamate, aspartate, malate, citrate and alanine. 4. The first stable products of [(14)C]bicarbonate fixation were malate and aspartate (containing between them over 90% of the total radioactivity fixed at the earliest times of sampling). 5. The percentage of the total radioactivity fixed that was contained in each of the radioactive compounds has been plotted against time. The slopes of the curves obtained show that hexose phosphates are primary stable products of [(14)C]methane and [(14)C]methanol incorporation and that aspartate and malate are primary stable products of [(14)C]bicarbonate incorporation. 6. No carboxydismutase activity has been found in cell-free extracts of the organism. This fact, together with the other findings, shows that an autotrophic metabolism involving the ribulose diphosphate cycle of carbon dioxide fixation cannot be operating.