Showing papers on "Yeast published in 1970"

Influence of environment on the content and composition of microbial free amino acid pools.

Abstract: SUMMARY: The free amino acid pool contents of Gram-negative bacteria (Aerobacter aerogenes, Erwinia carotovora, Pseudomonas fluorescens) were studied as functions of the growth environment and were compared with those from correspondingly grown cultures of Gram-positive bacteria (Bacillus subtilis var. niger, B. megaterium, B. polymyxa) and the yeast Saccharomyces cerevisiae. Although the pools of the Gram-positive bacteria and the yeast contained five to 20 times the concentration of free amino acids present in the pools of Gram-negative bacteria, all pools were similar in containing only a limited range of detectable amino acids. Glutamate invariably predominated and generally accounted for over 50% of the total amino acid content of the pool. The contents and composition of pools from micro-organisms maintained in steady states in chemostat cultures did not vary with time, but changed significantly with changes in either growth rate or the nature of the growth limitation. However, these pool variations were small compared with those resulting from addition of 2% (w/v) NaCl to a culture of growing bacteria. With cultures of Gram-negative bacteria, sudden changes in medium salinity effected marked and rapid changes in free glutamate content; with Gram-positive bacteria, similar changes occurred, but extremely slowly. Addition of 4% (w/v) NaCl to growing yeast cultures brought about no observed changes in pool size or composition. These results are discussed with reference to the involvement of free amino acids in synthesis and functioning of microorganisms.

3-phosphoglycerate kinase from rabbit sceletal muscle and yeast.

Abstract: Phosphoglycerate kinase, isolated from rabbit muscle in highly purified crystalline form, was compared in terms of chemical, physical and kinetic properties to yeast phosphoglycerate kinase A summary of the data is presented Both proteins are composed of a single polypeptide chain, and in electrophoresis only one band was found The N-terminus is masked The C-terminal amino acid of the muscle enzyme is valine Muscle and yeast enzyme have nearly identical molecular weights, Michaelis-Menten constants, optimal pH values and Vmax On the other hand, they differ significantly in their amino acid composition, especially in the content of sulfur and aromatic amino acids, in electrophoretic mobility and in heat stability The muscle enzyme has an essential SH group The single SH group of the yeast enzyme is apparently without importance for enzyme activity Differences in the same direction as those observed with yeast and muscle phosphoglycerate kinase are discussed in connection with other glycolytic enzymes from the same organisms

[3] The biochemical genetics of yeast

Abstract: Publisher Summary This chapter describes the techniques used in yeast ( Saccharomyces cerevisiae ) for the isolation of mutants and their biochemical characterization. Strains of Saccharomyces cerevisiae can be grown indefinitely either as haploids or as diploids. The wild-type yeast used in most genetic studies is of the haploid strain, α S288C. This is considered the standard type from which other strains can be derived. Haploid cells are generally smaller than diploids. Haploids mate on the appropriate medium to form the oval-shaped diploids. The diploids divide mitotically by budding. On sporulation medium, the diploids undergo meiosis and form four haploid spores in an ascus. Two of the ascospores are mating type a, and two are mating type α . The ascospores germinate into haploid cells, which divide by budding. The study of amino acid biosynthesis is facilitated by the use of mutants requiring the amino acid of interest. Many amino acid requiring mutants may be obtained from the stock collection. Mutants that are not available can be induced in the wild-type strain with a variety of mutagens. The standard treatment utilizes the potent mutagen, ethylmethanesulfonate (EMS). This procedure is convenient and gives high yields of mutants.

Periodic Density Fluctuation During the Yeast Cell Cycle and the Selection of Synchronous Cultures

Abstract: Yeast cells undergo periodic fluctuations in density during the cell division cycle such that a minimum in density occurs at the time of cell separation whereas a maximum occurs between the time of deoxyribonucleic acid replication and nuclear division. Synchronous cultures can be selected from asynchronously growing cell cultures by withdrawing the cells of least or greatest density after banding in Renografin-sucrose density gradients. This technique is rapid, reproducible, and almost unlimited in capacity.

Mating-Type-Dependent Inhibition of Deoxyribonucleic Acid Synthesis in Saccharomyces cerevisiae

Abstract: Yeast cells of mating type α excrete a sex factor which inhibits cell division and deoxyribonucleic acid replication but not ribonucleic acid or protein synthesis in cells of opposite mating type a.

Effects of High Levels of Yeast Feeding on Uric Acid Metabolism of Young Men

Abstract: THE possible use of single cells of yeast and bacteria as food is receiving much attention1,2. It has long been recognized3–9 that feeding yeast can increase urinary uric acid excretion, but the levels of its use in processed foods have been so low that no problems have arisen. If yeast and other single cells are used, however, as sources of protein rather than of vitamins, the intakes involved are much higher.

The isolation and crystallization of yeast and rabbit liver triose phosphate isomerase and a comparative characterization with the rabbit muscle enzyme.

Abstract: Triose phosphate isomerase was isolated from brewer's yeast and rabbit liver and was obtained in crystalline form. Chemical, physical and kinetic properties were compared to rabbit muscle triose phosphate isomerase. 1 The molecular weight of all three enzymes is in the range of 56000 to 60000. In dodecyl sulfate or as modified maleylated protein, the enzymes dissociate into two polypeptide chains each having a molecular weight in the range of 24000 to 29000. 2 The rabbit muscle and liver enzymes appear to be indistinguishable in terms of their amino acid composition, electrophoretic mobility, kinetic properties, inhibition sensitivity, pH optimum, molecular weight and N-terminal amino acid (alanine). 3 The yeast enzyme, on the other hand, was found different in the following respects; it has a several fold lower content of sulfur amino acids, is highly resistant to inactivation through photooxidation as well as sulfhydryl and alkylating agents. Furthermore, it contains different N-terminal amino acids (valine and alanine) and has kinetic properties differing from those of the rabbit enzymes. 4 The crystalline liver and muscle enzymes could be resolved into three distinct electrophoretic forms in starch and polyacrylamide gels. The possible interpretation of the multiple forms in terms of hybrids or conformers is discussed.

[119] l-glutamate dehydrogenases (yeast)

Abstract: Publisher Summary Two types of glutamate dehydrogenases are found in yeast. One is TPN + and triphosphopyridine nucleotide (TPNH) specific, and the second utilizes only the dinitrophenyl (DPN) forms. Both enzymes may be purified from the same yeast extract, although the DPN enzyme is present in higher concentrations when the yeast is grown on glutamate. This chapter describes the preparations for both enzymes for the same extract from Fleischmann's yeast cakes. Both enzymes are assayed by following the oxidation of the reduced coenzyme. In crude extracts, there is endogenous oxidation of both diphosphopyridine nucleotide (DPNH) and TPNH. All the purification steps of the DPN and TPN glutamate dehydrogenases are generally carried out at 0–4°. Both enzymes may be purified from the same yeast extract. The extract is clarified by addition of 1/40 volume of 1 M MnCl 2 and allowed to stand for 10 minutes and then centrifuged at 9,000 rpm for 10 minutes. The clarified extract shows no change in protein or enzymatic activity, but this clarification facilitates further fractionation by ammonium sulfate.

The Biogenesis of Yeast Mitochondria

Abstract: Publisher Summary This chapter discusses the aspects of the biogenesis of yeast mitochondria. The yeast cell has a number of features that make it ideally suited to the study of mitochondriogenesis. There are two major physiological control phenomena that may be experimentally exploited. Depending on the availability of oxygen, the yeast Saccharomyces cerevisiae can utilize a variety of substrates for growth. The fermentable sugars, such as glucose and galactose, can act as sole source of carbon and energy under both aerobic and anaerobic conditions. Aerobically grown S. cerevisiae contains typical mitochondria with the capacity for electron transport, oxidative phosphorylation, and the complete oxidation of pyruvate via the tricarboxylic acid cycle. Cells grown on slowly fermentable sugars, such as galactose, show intermediate respiratory activity. This phenomenon is known as glucose or catabolite repression and is similar to the repression of catabolic enzymes by glucose in bacteria.

Sexual reproduction in Candida lipolytica.

Abstract: Candida lipolytica is a rather common yeast isolated more frequently from substrates containing lipids or proteins, such as dairy products, than from substrates rich in sugars. This species assimilates hydrocarbons and is currently being studied for its potential to convert petroleum into yeast cells for use in feeds and foods. We have found C. lipolytica to exist in nature primarily in the heterothallic haploid state. When appropriate strains of opposite sex are mixed on a suitable sporulation medium, conjugation occurs followed by the production of ascospores. Since heterothallism permits laboratory control of hybridization, this characteristic of C. lipolytica enhances the possibility of im proving its strains for technological uses.

Secretion of cell-wall glycoproteins by yeast protoplasts. Effect of 2-deoxy-d-glucose and cycloheximide

Abstract: The effect of 2-deoxy-d-glucose and cycloheximide on the synthesis and secretion of the cell-wall constituents protein and mannan in yeast protoplasts was examined in detail. Although the 2-deoxy-d-glucose hardly influenced protein synthesis, a significant parallel inhibition of carbohydrate and protein secretion into the medium was observed. The mechanism of this inhibition is considered as an interference of metabolites of 2-deoxy-d-glucose with the synthesis of yeast mannan. Cycloheximide, which is an effective inhibitor of protein synthesis in yeast (Kerridge, 1958), inhibited the secretion of non-diffusible carbohydrate in yeast protoplasts, but on the other hand had no effect on the activity of particulate yeast mannan synthetase. Our results clearly show that blocking the synthesis of either part of the mannan–protein complex prevents the extracellular appearance of the other component. The nature of this phenomenon is discussed.

Proteolytic enzymes of Saccharomyces carlsbergensis.

Abstract: 1. Of four proteolytic enzymes isolated from autolysing Saccharomyces carlsbergensis, one is inactivated at about 45°C, whereas the others are stable at 50°C. pH optima for activity are from 3.0 to 8.0 but maximum stability is between pH6.0 and 6.5. All appear to be glycoproteins, the carbohydrate moiety containing glucose and mannose residues. 2. Lysed protoplasts of the same yeast release four proteolytic enzymes each of which have two pH optima at pH3.0 and 7.0 approximately. Compared with the enzymes from autolysed yeast, resistance to high temperature is much less, and they are not glycoprotein in nature. 3. The same yeast grown with N-acetyltyrosine ethyl ester as nitrogen source secretes into the medium four proteases believed to be glycoprotein in nature. Generally they resemble the enzymes from lysed protoplasts more than those from autolysing yeast.

The separation of β-glucanases produced by Cytophaga johnsonii and their role in the lysis of yeast cell walls

Abstract: 1. When Cytophaga johnsonii was grown in the presence of suitable inducers the culture fluid was capable of lysing thiol-treated yeast cell walls in vitro. 2. Autoclaved or alkali-extracted cells, isolated cell walls and glucan preparations made from them were effective inducers, but living yeast cells or cells killed by minimal heat treatment were not. 3. Chromatographic fractionation of lytic culture fluids showed the presence of two types of endo-beta-(1-->3)-glucanase and several beta-(1-->6)-glucanases; the latter may be induced separately by growing the myxo-bacterium in the presence of lutean. 4. Extensive solubilization of yeast cell walls was obtained only with preparations of one of these glucanases, an endo-beta-(1-->3)-glucanase producing as end products mainly oligosaccharides having five or more residues. Lysis by the other endo-beta-(1-->3)-glucanase was incomplete. 5. The beta-(1-->6)-glucanases produced a uniform thinning of the cell walls, and mannan-peptide was found in the solution. 6. These results, and the actions of the enzyme preparations on a variety of wall-derived preparations made from baker's yeast, are discussed in the light of present conceptions of yeast cell-wall structure.

Amino‐acylation du tRNA1Val de Escherichia coli par la phéenylalanyl‐tRNA synthétase de levure

Abstract: Comparison of the known primary structures of several tRNAs reveals striking similarities between the nucleotide sequences of yeast tRNAphe and Escherichia coli tRNA1Val. On the assumption that such structural analogy might lead to aminoacylation of both tRNAs by each of the corresponding aminoacyl-tRNA synthetases, a detailed study of this system was undertaken. The results indicate that under optimal conditions, E. coli tRNA1Val can be completely aminoacylated by yeast phenylalanyl-tRNA synthetase, while the reciprocal (i.e. valyl-tRNAPhe (yeast) formation by E. coli valyl-tRNA synthetase) could not be demonstrated under any of a variety of conditions tested. Conditions for Phe-tRNA1Val (E. coli) formation by yeast phenylalanyl-tRNA synthetase differ radically from those leading to aminoacylation of tRNA in homologous systems. In particular, the final yield of aminoacyl-tRNA varies with enzyme concentration and is markedly affected by the nature of the buffer and the pH, as well as by the presence of monovalent cations and organic solvents such as ethanol and dimethyl sulfoxide. Similar observations have already been reported in the study of the aminoacylation of tRNA in several heterologous systems. The results are discussed in relation to the structure of the two tRNAs.

Specific inactivation of yeast hexokinase induced by xylose in the presence of a phosphoryl donor substrate.

Abstract: Yeast hexokinase can be inactivated by xylose in the presence of MgATP. The effect is highly specific for xylose. The nucleotide and divalent metal specificities are similar to those of the hexokinase reaction. The dissociation constants, as deduced from the effect of the concentration of the inactivating agents on the rate of inactivation, are about 0.2 mM for MgATP and about 10 mM for xylose. These values are similar to the Michaelis constant and Ki value for these compounds as substrate and competitive inhibitor, respectively, in the hexokinase reaction. Sugars capable of binding at the sugar substrate subsite protect against xylose-induced inactivation with efficiencies closely related to their respective Ks or Ki values. The dissociation constant of glucose, as deduced from its protective effect, is about 0.04 mM. When resting yeast is incubated aerobically with 0.1 M xylose and 1% ethanol, a marked loss of hexokinase activity takes place. Among the possible mechanisms of this irreversible inactivation there is evidence against the involvement of phosphorylation or glycosylation of the protein as well as of a change in its degree of polymerization.

Induction and repression of arginase and ornithine transaminase in baker's yeast.

Abstract: The arginase and the ornithine transaminase of baker's yeast are induced byl-arginine. Both enzymes have been shown to be repressed by nitrogen compounds. This is evidenced primarily by the decrease in specific enzyme activities caused by the addition of readily assimilable nitrogen compounds to a yeast culture with arginine, secondly by the derepression of both enzymes during nitrogen starvation of the yeast grown in various arginine-free media. This derepression equals both in rate and in amount the enzyme synthesis during the adaptation of the yeast to a medium withl-arginine as the sole nitrogen source. It is inhibited by various assimilable and non-assimilable amino acids. The derepression is the result of the nitrogen deficiency itself, since during the starvation of the yeast for sulphate, phosphate or magnesium, neither of the two enzymes is derepressed, and since it is independent of the nature of the carbon source in the nitrogen starvation medium, provided the latter is immediately assimilable.