Phosphatase synthesis in Klebsiella (aerobacter) aerogenes growing in continuous culture

1. Phosphatase synthesis was studied in Klebsiella aerogenes grown in a wide range of continuous-culture systems. 2. Maximum acid phosphatase synthesis was associated with nutrient-limited, particularly carbohydrate-limited, growth at a relatively low rate, glucose-limited cells exhibiting the highest activity. Compared with glucose as the carbon-limiting growth material, other sugars not only altered the activity but also changed the pH-activity profile of the enzyme(s). 3. The affinity of the acid phosphatase in glucose-limited cells towards p-nitrophenyl phosphate (K(m) 0.25-0.43mm) was similar to that of staphylococcal acid phosphatase but was ten times greater than that of the Escherichia coli enzyme. 4. PO(4) (3-)-limitation derepressed alkaline phosphatase synthesis but the amounts of activity were largely independent of the carbon source used for growth. 5. The enzymes were further differentiated by the effect of adding inhibitors (F(-), PO(4) (3-)) and sugars to the reaction mixture during the assays. In particular, it was shown that adding glucose, but not other sugars, stimulated the rate of hydrolysis of p-nitrophenyl phosphate by the acid phosphatase in carbohydrate-limited cells at low pH values (<4.6) but inhibited it at high pH values (>4.6). Alkaline phosphatase activity was unaffected. 6. The function of phosphatases in general is discussed and possible mechanisms for the glucose effect are outlined.

Interaction of maltose transport with the transport of glucose and galactosides

In cells of Escherichia coli possessing both maltose and galactoside permease, fluxes via one permease are independent of the substrate for the other permease. However, both fluxes are partially inhibited by glucose or alpha-methyl glucoside at low concentrations in cells grown on glucose. Neither maltose nor galactosides have an inhibitory effect on glucose permease function. These observations are consistent with the hypothesis that the number of glucose permease systems on the cell surface of such cells is much larger than the number for maltose or galactosides.

Influence of cellobiose on the colonial morphology and glycosidases of several fungi

Several fungi were screened for biochemical and morphological responses to cellobiose, glucose, and maltose. All of the fungi contained an enzyme(s) capable of hydrolyzing an alkali-insoluble cell wall component from their respective hyphae. These enzymes as well as α- and β-glycosidases and N-acetyl-β-D-glucosaminidases were subject to regulation by carbohydrates in the medium. Cellobiose induced gross and microscopic morphological changes in the basidiomycetes but not in the ascomycetes or phycomycetes. Cellobiose also increased the specific activity of the wall-hydrolyzing enzymes in the basidiomycetes. The relationships between the carbon source, wall-hydrolyzing enzymes, and morphological responses are discussed.

Dissimilation of methionine by fungi

Soil fungi that attacked methionine required a utilizable source of energy such as glucose for growth. This is an example of co-dissimilation. Experiments with one of the fungi, representative of the group, are reported. In the absence of glucose, pregrown mycelium, even when depleted of energy reserves, oxidatively deaminated methionine with accumulation of alpha-keto-gamma-methyl mercapto butyric acid and alpha-hydroxy-gamma-methyl mercapto butyric acid. When glucose was provided, all of the sulfur of methionine was released as methanethiol, part of which was oxidized to dimethyl disulfide. No sulfate, sulfide, or hydrosulfide products were detected. Evidence was obtained that deaminase and demethiolase were constitutive. Deamination preceded demethiolation and alpha-keto butyric acid accumulated as a product of the two reactions. Other carbon residues were alpha-hydroxy butyric acid and alpha-amino butyric acid. Inability of the fungus to metabolize alpha-keto butyrate was responsible for its inability to utilize methionine as a source of carbon and energy. Several other fungi isolated from soil grew on alpha-amino butyrate but could not grow on methionine owing to inability to demethiolate it.

Dextran-induced agglutination of Streptococcus mutans, and its potential role in the formation of microbial dental plaques

Glucose-grown washed cells of streptococci similar to Streptococcus mutans, which contain cell-bound dextransucrase, have been observed to agglutinate upon the addition of high molecular weight dextran. Low molecular weight dextran or unrelated polysaccharides were ineffective. Agglutination also occurred upon addition of sucrose, which can be converted into dextran, but not with other mono- and disaccharides. Other bacteria, including species capable of synthesizing dextrans, were not observed to exhibit this phenomenon. Cells of S. mutans agglutinated upon addition of dextran over a wide pH range, but maximal sensitivity to dextran occurred at pH 8.5. At this pH, such cells can be used for a simple, specific, and exquisitely sensitive qualitative assay for high molecular weight dextran, for addition of 6 ng of dextran with a molecular weight of 2 x 10(6) (i.e., approximately three molecules per cell) caused detectable agglutination. High concentrations of glucose, levan, and dextran of molecular weight of 2 x 10(4) inhibited the reaction. Fluorescein-labeled cells of S. mutans were observed to adhere to dextran-containing plaques and dextran-treated teeth, suggesting that this phenomenon may be of importance in the formation of streptococcal dental plaques. The mechanism responsible for dextraninduced agglutination appears to involve the affinity of a receptor site, possibly dextransucrase, on the surface of several cells for common dextran molecules.

Control of jejunal sucrase and maltase activity by dietary sucrose or fructose in man. A model for the study of enzyme regulation in man

The specific effect of dietary sugars on jejunal disaccharidase activity in seven normal nonfasted male volunteers was studied. The sugars tested were sucrose, maltose, lactose, glucose, fructose, and galactose. Comparisons were made of the effects of each sugar in an isocaloric liquid diet. In all subjects, sucrose feeding, as compared to glucose feeding, significantly increased jejunal sucrase (S) and maltase (M) activities, but not lactase (L) activity. The S/L and M/L ratios increased to a significant degree. Fructose feeding, in two subjects, gave results similar to sucrose when comparing fructose and glucose diets. One subject was fed lactose, galactose, and maltose. These sugars, compared to glucose, did not increase disaccharidase activity. Fructose appears to be the active principle in the sucrose molecule. These results demonstrate that specific dietary sugars can alter enzyme activity in the small intestine of man in a specific fashion. Sucrose and fructose are able to regulate sucrase and maltase activity. Dietary alteration of intestinal enzymes may represent a suitable system for studying the regulation of enzyme activity in man.

Stimulation of the labellar sugar receptor of the fleshfly by mono- and disaccharides

Responses of the labellar sugar receptor of the fleshfly, Boettcherisca peregrina, were studied over a wide range of concentrations of several sugars (sucrose, maltose, glucose, fructose, and mannose) in single solutions and in mixtures. The results suggest (a) that the receptor sites are not completely differentiated for glucose and for fructose combination, (b) that the receptor site is composed of two subunits. Such suggestions are based on the classical model, where the response is proportional to the number of the sites, two subunits of each site being simultaneously occupied with one molecule of disaccharides or two molecules of monosaccharides. It is shown, however, that an allosteric model gives a somewhat better interpretation of the experimental results.

Effects of amino acids, dipeptides and disaccharides on the electric potential across rat small intestine

1. The effects of a number of amino acids, peptides and disaccharides on the potential difference across the wall of the rat small intestine have been studied.2. All the L-amino acids tested, except lysine and arginine, and the three D-amino acids tested stimulate the potential when present in the mucosal fluid.3. The concentration dependence and time course of the potential differs between different amino acids.4. The results suggest a close correlation between the active transport of an amino acid and the potential change which it evokes.5. Glycyl-glycine, glycyl-L-alanine and tri-glycine stimulate the potential and this appears to be due to the amino acids liberated by hydrolysis.6. Maltose and sucrose, but not lactose, stimulate the potential, and the effect appears to depend on the extent of hydrolysis of the disaccharide.7. The magnitude of the potential varies in different parts of the intestine. For the amino acids tested the maximum potential occurred in the distal ileum, while in the case of hexoses the maximum potential was found in the mid-intestine.8. The results are discussed in relation to the mechanisms of transfer of hexoses and amino acids.

Metabolism of the reserve polysaccharide of Streptococcus mitis. Some properties of a pullulanase

1. A pullulanase has been separated from cell extracts of Streptococcus mitis. The enzyme was freed from transglucosylase by fractionation with ammonium sulphate. 2. Pullulanase was produced in the absence of inducers, and addition of glucose or maltose to the broth did not increase the yield of enzyme. 3. The pullulanase acted rapidly on alpha-(1-->6)-bonds in substrates having the structure alpha-maltodextrinyl-(1-->6)-maltodextrin, but had no action on isomaltose, 6-alpha-glucosylmaltodextrins or 6-alpha-maltodextrinylglucoses. 4. 6-alpha-Maltotriosylmaltodextrins were hydrolysed over 10 times faster than 6-alpha-maltosylmaltodextrins. 5. The branch linkages of amylopectin phosphorylase limit dextrin, glycogen phosphorylase limit dextrin and glycogen beta-amylase limit dextrin were hydrolysed. The action of pullulanase on amylopectin and glycogen was accompanied by a rise in the iodine stain of 50% and 30% respectively. 6. A reversal of pullulanase action occurred on incubation with high concentrations of maltotriose. Condensation of maltosyl units to form a branched tetrasaccharide occurred less readily. 7. S. mitis pullulanase was rapidly inactivated at temperatures higher than 40 degrees , and the enzyme did not recover activity on storage at room temperature.

The slowing of gastric emptying by monosaccharides and disaccharides in test meals

1. Test meals containing various concentrations of glucose, maltose, sucrose, fructose, lactose, galactose and mixtures of these solutes were given to six healthy subjects. All meals contained 40 mM sodium citrate.2. The slowing of gastric emptying produced by the disaccharides in test meals was generally consistent with the stimulation of duodenal osmoreceptors occuring after the hydrolysis of the disaccharides.3. Glucose was slightly more effective, per osmole, in slowing gastric emptying than was galactose.4. By comparison with glucose or galactose, fructose was much less effective in slowing gastric emptying. In three subjects out of six there was a threshold for its effect.5. The results may be indicative of the relative activities of disaccharidases in the brush border of the small intestine. They are consistent with there being an osmoreceptor deep to these enzymes which slows gastric emptying.

Glucosidases and exo-glucanases

A comparison was made of exo-α-glucanases with α-glucosidases, and of exo-β1 → 3-glucanases with β-glucosidases to establish criteria for their characterization. Dimers, trimers, and tetramers of glucose are substrates for both exo-glucanases and glucosidases. Exo-glucanases act more rapidly on the longer oligomers, glucosidases on the shorter. Exo-glucanases act with inversion of configuration, glucosidases with retention. Other differences are found in transfer activity, in degree of specificity, and in susceptibility to various inhibitors.

Inhibition of sucrose phosphatase by sucrose

1. Partially purified sucrose phosphatase from immature stem tissue of sugarcane is inhibited by sucrose. The enzyme was also inhibited by maltose, melezitose and 6-kestose but not by eight other sugars, including glucose and fructose. 2. The relative effectiveness of sucrose, maltose and melezitose as inhibitors is different for sucrose phosphatase from different plants. 3. The inhibition of the sugar-cane enzyme by sucrose was shown to be partially competitive. The K(i) for sucrose is about 10mm. 4. Melezitose is also a partially competitive inhibitor of the enzyme but the inhibition by maltose is probably mixed. 5. The possibility that sucrose controls both the rate of accumulation of sucrose in stems of sugar-cane and sucrose synthesis in leaves by inhibiting sucrose phosphatase is discussed.

Regulation of proteinase formation in a species of Micrococcus

Micrococcus sp. ATCC No. 407 (M. freudenreichii) produced relatively large amounts of extracellular proteinase in synthetic medium containing methionine, thiamine, biotin, NH4Cl, NaHCO3, NaCl, MgSO4, and FeSO4, with aspartic acid, asparagine, glutamic acid, or glutamine as the carbon source. The organism produced relatively small amounts of proteinase with succinate, malate, fumarate, maltose, maltotriose, or maltotetraose as the carbon source. In synthetic medium containing maltose, any one of several amino acids stimulated growth and proteinase production. The results indicated that the organism is a partial constitutive strain with respect to proteinase production and suggested that proteinase formation is controlled by a form of end-product induction. In the presence of inducer, carbon sources such as succinate or maltose caused suppression of proteinase formation, suggesting control by metabolic repression as well. Because extracellular proteinase formation is induced by amino acids and suppressed by carbon sources such as succinate or maltose, and because the organism can utilize amino acids as carbon sources for growth, it. is suggested that the function of extracellular proteinase in this organism is to ensure a supply of carbon for growth rather than a supply of amino acids for protein synthesis.

The use of monosaccharides, disaccharides, and trisaccharides in synthetic dilutents for the storage of ram spermatozoa at 37 degrees-C and 5 degrees-C

Using synthetic semen diluents based on 20 mM phosphate buffer, 31 Mm N aCl, 0�8 % non.dialysable skim milk solids, plus antibiotics, and 185 mM of the sugars ribose, arabinose, xylose, glucose, mannose, fructose, galactose, rhamnose, maltose, lactose, sucrose, or raffinose, it was found that ram spermatozoa survive best at 37�C in diluents containing glucose, mannose, fructose, or sucrose; however, at 5�C ribose, arabinose, xylose, and galactose were the sugars of choice. Increasing replacement of fructose in the diluent with up to 185 mM of these sugars resulted in increased survival at the respective temperatures. Part replacement of 185 mM fructose in the range 7�75-62 mM with the sugars most favourable at 5�C was of little benefit. No effect of changes in osmotic pressure was noted using varying concentrations of the sugars to give tonicities of 0�9, 1� 0, and 1 �1 relative to 154 mM NaCI or 308 mM sugar. Increased motility scores and percentages of motile sperma� tozoa were observed when 17 mM fructose was added to ribose and arabinose diluents at 5�C, but not when added to diluents containing xylose, the hexoses, galactose, fructose, and glucose; nor for any sugar� containing diluent at 37�C.

Toxigenicity of Clostridium histolyticum

Nishida, Shoki (Kanazawa University, Kanazawa, Japan), and Masaaki Imaizumi. Toxigenicity of Clostridium histolyticum. J. Bacteriol. 91:477-483. 1966.-From 234 soil samples, 21 strains of Clostridium histolyticum of different levels of alpha-toxigenicity were isolated by a new method specially designed for the isolation of this species. The alpha-toxigenicity of freshly isolated strains and of stock strains was closely associated with the potentiality for sporulation, growth, and smooth-colony formation. The presence of sugars, particularly xylose and arabinose, was inhibitory for growth. A few controversies on the biological properties of this species seem to be due to disregard for the growth-inhibiting effects of these sugars.