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Biomedical subjects

S Bauer

Publications and source records attributed to S Bauer.

At least 217 records · Page 12Linked to original sources
PubMed1976

Interaction of concanavalin A with external mannan-proteins of Saccharomyces cerevisiae. Glycoprotein nature of beta-glucanases.

beta-Glucanases secreted into culture fluid by protoplasts or intact cells of the yeast Saccharomyces cerevisiae were investigated for the presence of covalently linked carbohydrates. Gel filtration of the enzymes on Biogel A-1.5m showed that endo-beta-1,3-glucanase is a polydisperse enzyme of high-molecular weight which elutes in about the same volume as external yeast invertase. Exo-beta-glucanase was eluted from the gel as a much lighter enzyme. Endo-beta-1,3-glucanase added to a mixture of extracellular mannoproteins was precipitated by concanavalin A to a similar extent to mannan, invertase and acid phosphatase. Under the same conditions exo-beta-glucanase did not interact with the lectin, but was partially precipitated from the solution in the absence of foreign mannan or mannan-proteins. The results show that endo-beta-1,3-glucanase of S. cerevisiae is a mannoprotein of a similar nature to external invertase and acid phosphatase. However, exo-beta-glucanase appears to be a glycoprotein which does not contain the highly branched mannan polymer in its molecule.

Acid Phosphatase↗
PubMed1976

Biosynthesis of yeast mannan. Diversity of mannosyltransferases in the mannan-synthesizing enzyme system from yeast.

1. A microsomal enzyme preparation from the yeast Saccharomyces cerevisiae catalyzes the transfer of mannosyl units from GDPmannose to mannose and a number of mannose-containing oligosaccharides and glycosides whereby different glycosidic bonds are formed. 2. Of the compounds tested besides mannose, only those containing an alpha-linked mannosyl unit at the nonreducing position of their molecule were effective as acceptors. Monodeoxyanalogues of mannose as well as alpha-mannose phosphates did not serve as acceptors in the above reaction. 3. The structure of the product formed with mannose as acceptor was determined to be O-alpha-D-mannosyl-(1 leads to 2)-mannose; with alphaMan (1 leads to 6)mannose as the acceptor, the product was alphaMan(1 leads to 6)mannose and with alphaMan-(1 leads to 2)mannose the product was tentatively characterized as a mixture of alphaMan-(1 leads to 3)alphaMan(1 leads to 2)mannose and alphaMan(1 leads to 2)alphaMan(1 leads to 2)mannose. 4. The enzymes catalyzing the formation of different types of glycosidic bonds differed in their acceptor specificity, pH-activity curves and rates of heat denaturation. 5. Radioactive disaccharides were unable to enter the mannan protein molecule in the cell-free system while free radioactive mannose did incorporate into polysaccharide to a minor extent under the same conditions.

Enzyme Activation↗
PubMed1976

Biosynthesis of yeast mannan. Independent formation of two carbohydrate moieties in the mannoprotein molecule.

The formation of two distinct types of carbohydrates moieties, beta-elminable saccharides attached to serine and/or threonine and of the polysaccharide portion of yeast mannan-protein was investigated using the particulate mannan synthetase from Saccharomcyes cerevisiae and GDP-[U-14C]mannose as mannosyl donor. The accumulated evidence obtained by following the kinetics of mannose incorporation into the different carbohydrate portions of mannoprotein, kinetics of thermal denaturation of enzymes responsible for their synthesis and by "pulse-chase" experiment where the change in the distribution of incorporated radioactivity was followed between the two carbohydrate moieties strongly suggests that the two carbohydrate portions in yeast mannoprotein are being synthesized independently, most probably by different sets of enzymes. At the same time, the obtained data show the beta-eliminable saccharides attached to serine and threonine in the peptide do not serve as precursors in the formation of polysaccharide part of mannoprotein.

Drug Stability↗
PubMed1976

Transglycosylic reactions of nucleotides of deoxy sugars. Biosynthesis of deoxy analogues of alpha,alpha'-trehalose.

The biosynthesis of alpha,alpha'-trehalose was investigated in a reaction catalyzed with yeast UDP-Glc :glucose-6-phosphate 1-glucosyl transferase. It was revealed that the hydroxyls at positions C-2, C-3, C-4 and C-6 are not essential for preserving its substrate properties in this reaction. The affinity of the enzyme and the rate of hexose incorporation into trehalose decreases in following sequence: UDP-glucose, UDP-2-deoxy-D-glucose, UDP-6-deoxy-d-glucose, UDP-4-deoxy-D-glucose and UDP-3-deoxy-D-glucose.

Deoxy Sugars↗
PubMed1976

Dense growth of aerobic bacteria in a bench-scale fermentor.

Escherichia coli B, Escherichia coli MRE 600, Escherichia coli K 12-3300, Pseudomonas fluorescens, and Aerobacter aerogenes were grown exponentially in a bench-scale fermentor to cell concentrations in the range of 20 to 41 g dry cells/liter at 30 degrees C and 30 to 55 g dry cells/liter at 25 degrees C. The high cell concentrations were achieved in a growth system previously described for growth of Escherichia coli W (Biotechnol. Bioeng., 16, 933 (1974); ibid. 17, 227 (1975)). Various enzyme activity levels in the high-concentration cells were compared to those in cells grown in conventional low-density cultures. No significant differences were found. The culture supernatants were found to be essentially free of high-molecular weight metabolic or cell lysis products. Yield constants for glucose, nitrogen, oxygen, and phosphorus were also determined in the dense cultures and some of their relations to the growth conditions are discussed.

Aerobiosis↗
PubMed1976

Pilot scale exponential growth of Escherichia coli W to high cell concentration with temperature variation.

An efficient method to grow Escherichia coli W to high cell concentrations on the pilot scale is described and discussed. The method involves growth linked introduction of glucose and ammonia to the culture, sparging with oxygen, and maintenance of aerobic conditions by gradually decreasing the temperature in the culture in order to keep the oxygen demand within the limits of the capacity of supply. Under these conditions the linear rate of cell mass production is actually the result of exponential growth with a gradually decreasing growth-rate constant. About 10 kg packed cells were produced in a 50 liter working-volume fermentor in one run of 13 hr. The concentration of the cells at the end of the growth was about 47 g dry cells/liter. The expenditure for nutrients was minimal and the controls were of simple automatic nature. From the determined yield constants for glucose, nitrogen, phosphorus, and oxygen it may be inferred that the cells grown by this method are similar to those grown exponentially at constant temperature.

Bacteriological Techniques↗
PubMed1976

Biosynthesis of yeast mannan. Characterization of mannan-synthesizing enzyme systems from mutants defective in mannan structure.

The yeast Saccharomyces cerevisiae X2180-1A (wild) and its mutants X2180-1A-4 (mnn 1) and X2180-1A-5 (mnn 2) defective in mannan biosynthesis were used as enzyme sources to catalyze in vitro mannosyl transfer from GDP-[14C-U]-mannose to endogenous glycoproteins as well as to exogenous, low-molecular weight acceptors. While the enzyme preparation from the wild strain exhibited all mannosyl transferase activities involved in mannan biosynthesis by catalyzing the synthesis of characteristic mannoprotein, the enzyme from mnn 1 mutant failed to catalyze the synthesis of alpha(1 leads to 3) mannoside linkages both with endogenous as well as with exogenous acceptors. The enzyme preparation from the mnn 2 mutant catalyzed the formation of mannoprotein very similar to that obtained with the enzyme from the wild strain. The most important difference was the formation of a higher number of unsubstituted mannosyl units in the alpha(1 leads to 6) linked mannan backbone. The observed results support the hypothesis that in the mnn 1 the mutation has altered the structural gene involved in biosynthesis of an alpha(1 leads to 3) mannosyl transferase catalyzing the addition of alpha(1 leads to 3) linked mannosyl units to alpha(1 leads to 2) linked mannotrioses in the polysaccharide side chains and in the oligosaccharides attached to serine and/or threonine in the protein part of mannan molecule. The mnn 2 mutant represents most probably a kind of regulatory mutation where the activity of an alpha(1 leads to 2) mannosyl transferase adding the mannosyl units directly to alpha(1 leads to 6) linked backbone in the outer region of polysaccharide part of yeast mannan is repressed in vivo but becomes significant in vitro.

Electron Transport↗
PubMed1975

Wall mannan of Saccharomyces cerevisiae. Metabolic stability and release into growth medium.

Selective labelling of cell wall mannan with radioactive precursors in growing Saccharomyces cerevisiae showed that this polysaccharide is metabolically stable during exponential growth. Mannan once inserted into the wall is not subject to turnover or release into the growth medium. However, about 10% of the amount of mannan incorporated into the cell wall fraction can be recovered in the non-dialyzable material isolated from the growth medium. Therefore, the mannan escaping from the cell must be either a mannan de novo synthesized, not trapped in the growing wall structure, or a mannan with a non-structural role. Radioactivity was also retained in the wall fraction of cells pre-labelled with [14C] glucose which pointed to metabolic stability of all cell wall polysaccharides in growing S. cerevisiae.

Cell Wall↗
PubMed1975

Uridine diphosphate 2-deoxyglucose. Chemical synthesis, enzymic oxidation and epimerization.

The paper describes chemical synthesis of uridine diphosphate 2-deocyglucose (UDPdGLc) through reaction of uridine 5'-phosphomorpholidate with 2-deoxy-a-D-glucopyranosyl phosphate. The prepared analog of uridine diphosphate glucose (UDPGlc) served as a substrate for calf liver UDPGlc dehydrogenases (EC 1.1.1.22), the reaction product was identified as nucleotide deoxyhexuronic acid derivative. The apparent Km for UDPdGlc was found to be 60 times that of UDPGlc, and the relative V value for the analog was 0.09. The peculiar lag-eriod in reaction kinetics has been observed for the analog and is presumably connected with the slow rate of the initial stages of the reaction. UDPdGlc was found to be quite an efficient substrate for UDPGlc 4-epimerases (EC 5.13.2) from yeast, calf liver and mung bean seedlings.

Alcohol Oxidoreductases↗
PubMed1975

The influence of the peptide chain length on the activity of peptidyl-tRNA hydrolase from E. coli.

The dependence of the Vmax and Km on the length of the peptide moiety in the peptidyl-tRNA series (Gly)n-Val tRNA, was measured in the system peptidyl-tRNA hydrolase-peptidyl-tRNA. It was found that the Km value decreases from 7.2 X 10-7 M for Gly-Val-tRNA to 4.6 X 10-7 M FOR (Gly)2-Val-tRNA and to 1.7 X 10-7M for (Gly)3-Val-tRNA; further increase of the peptide chain is not followed by decrease of the Km. The Vmax values are 5.7 pmole/min/EU for Gly-Val-tRNA and 42 pmole/min/EU for (Gly)3-Val-tRNA. The enzyme activity is inhibited competitively by uncharged tRNA with a KI value of about 10-5M. The significance of these results described in this paper, in relation to the fact that peptides and peptide esters do not inhibit the enzyme activity, and in relation to the proposed physiological role of the enzyme, is discussed.

Carboxylic Ester Hydrolases↗
PubMed1975

Mechanism of 2-deoxy-D-glucose inhibition of cell-wall polysaccharide and glycoprotein biosyntheses in Saccharomyces cerevisiae.

The mechanism of inhibition by 2-deoxy-D-glucose of the synthesis of yeast wall polysaccharides and glycoproteins was investigated in Saccharomyces cerevisiae cells and protoplasts. The extent of the inhibition of mannan and glucan synthesis was found to be dependent on whether glucose or mannose was used as the carbon source in the medium. During growth on glucose, 2-deoxy-D-glucose inhibited more intensively mannan than glucan formation. Biosynthesis of wall glucan was strongly suppressed in mannose medium. Selective incorporation of 2-deoxy-D-glucose occurred into that polysaccharide, synthesis of which was more inhibited under given conditions. Suggestive evidence has been obtained that the decisive factor for the proportion of glucan and mannan in the walls is the direction of glucose 6-phosphate/mannose 6-phosphate interconversion dependent on the exogeneous hexose. No close correlation was found between the inhibition of mannan synthesis and the appearance of the mannan-protein enzymes invertase and acid phosphatase. Effect of 2-deoxy-D-glucose was therefore investigated on the parallel synthesis of protein, mannan and several extracellular and intracellular enzymes in protoplasts grown on glucose and mannose. The results obtained pointed out that the hindrance of the secretion of mannan-protein enzymes is of a complex nature and related more to the inhibition of synthesis of the protein moiety than to the inhibition of glycosylation. Synthesis of several enzymes was found to be a subject of a metabolic control by 2-deoxy-D-glucose or its metabolites.

Acid Phosphatase↗
PubMed1975

The technique and results of pyleocalycotomy for staghorn calculi.

In 10 kidneys treated by the sinus approach the overall recurrence rate was 40%. In 48 kidneys treated by pyelocalycotomy the overall recurrence rate was 17% but only 6% in functioning kidneys with infective stones. Infection was controlled in 75% of patients from whom all stone fragments were removed radiologically but all patients in whom fragments remained, or who developed further calculi, remained infected--with Proteus in 75% of cases. All patients with kidneys completely cleared of calculi in whom infection was controlled remained stone-free for periods up to 10 years.

Adult↗