Isolation of yeast with killer activity and its breeding with an industrial baking strain by protoplast fusion

Summary Wild strains of Saccharomyces cerevisiae were isolated from dairy products, bakery goods, fresh fruit and vegetables, and tested for killer activity. Four isolates out of 238 strains possessed killer activity. The best of these was converted to the petite form and hybridized with an industrial strain of Saccharomyces cerevisiae by protoplast fusion. Thirty-eight out of 104 isolates had killer activity, and some of these had good dough-raising activity as well.     

The anthranilate aggregate of Escherichia coli: kinetics of inhibition by tryptophan of phosphoribosyltransferase

The kinetic mechanism of the phosphoribosyltransferase reaction is shown to be rapid equilibrium random bi bi with an enzyme-anthranilate-pyrophosphate abortive complex. We present a rate equation that not only predicts the observed kinetic patterns but also accommodates the fact that feedback inhibition is partial, even though tryptophan (Ki = 0.5 microM) and phosphoribosylpyrophosphate (Km = 50 microM) are competitive. Neither ligand completely abolishes the effect of the other. Instead, the binding of one ligand leads to a mutual elevation in the dissociation constant of the opposing ligand by a factor of two to three. Tryptophan inhibition is noncompetitive with respect to anthranilate (Km = 0.58 microM) and does not diminish the rate of interconversion of ternary complexes. Tryptophan cooperativity, with respect to the inhibition of phosphoribosyltransferase, conforms to the concerted Monod-Wyman-Changeux formulation (kinetic Hill coefficient = 2), whereas tryptophan as an inhibitor of anthranilate synthase more closely conforms to a Koshland model of sequential cooperativity with a kinetic Hill coefficient of 1.4. The aggregate contains only one class of tryptophan sites. Thus the first tryptophan molecule bound to the aggregate maximally inhibits both phosphoribosyltransferase active centers and one of the two anthranilate synthase catalytic sites. The remaining anthranilate synthase subunit thereupon is converted into a form with less (but not zero) affinity for chorismate and a greater affinity for a second molecule of tryptophan.     

Purification and characterization of a calmodulin-dependent kinase from rat brain cytosol able to phosphorylate tubulin and microtubule-associated proteins

Tubulin is a major substrate for endogenous Ca2+-calmodulin-dependent phosphorylation in synaptic cytoplasm. The present study details the purification to apparent homogeneity and characterization of a brain cytosolic Ca2+-calmodulin-dependent kinase which phosphorylates tubulin and microtubule-associated proteins as major substrates. The cytosolic kinase system, purified by sequential chromatography on phosphocellulose resin, calmodulin-affinity resin, and Fractogel TSK HW-55, chromatographs as a homogeneous complex of approximately 600,000 Da on Sephacryl S-300. This calmodulin-dependent kinase possesses a group of properties which specifically characterize this enzyme system: 1) the enzyme contains two calmodulin-binding doublets, rho and sigma, of approximately 52,000 and 63,000 Da, respectively; 2) both the rho and the sigma subunits demonstrate isoelectric points between 6.7 and 7.2; 3) both the rho and sigma subunits demonstrate autophosphorylation; 4) both the rho and sigma subunits show significant homologies as assessed by tryptic peptide fingerprints; 5) in the absence of substrate, both the rho and sigma subunits manifest lower mobility autophosphorylated species; 6) the kinase phosphorylates beta-tubulin equally on threonine and serine residues. Substrate specificity, kinetic parameters, calmodulin-binding properties, subunit composition, and subunit isoelectric points clearly differentiate this enzyme from other previously reported calmodulin-dependent kinases.     

Genetic Analysis of Murine Arylsulfatase C and Steroid Sulfatase

SWR/J mice possess two- to threefold higher 4-methylumbelliferyl sulfate (4MUS), dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E1S) sulfatase activities in liver and kidney extracts than do A/J mice. These interstrain activity differences are maintained throughout the 6- to 45-day postnatal period. Characteristics of the hepatic activities of SWR/J mice suggest that all three activities reside in the same enzyme. Biochemical properties of the SWR/J and A/J enzyme were not significantly different. Expression of hepatic enzyme activity is subject to regulation by an autosomal locus possessing two alleles with additive effects. Postnuclear E1S- and DHEAS-sulfatase activities are primarily microsomal. Although postnuclear hepatic 4MUS-sulfatase activity is predominantly microsomal, renal activity is primarily nonmicrosomal. Only that portion of 4MUS-sulfatase occurring in cell membranes appears capable of hydrolyzing E1S and DHEAS. The hepatic- and renal-specific subcellular distributions of 4MUS-sulfatase activity may reflect tissue differences in enzyme processing. Renal 4MUS-sulfatase activity is also controlled by an autosomal gene with two alleles having additive effects. Positive correlation between hepatic and renal 4MUS-sulfatase activities indicates that both activities are most likely influenced by the same gene.     

Iron-Chelating Compounds Produced by Soil Pseudomonads: Correlation with Fungal Growth Inhibition

Strains of Pseudomonas putida, Pseudomonas sp., and Pseudomonas aeruginosa were examined for their ability to grow in the presence of the iron chelator, ethylenediamine-di-(o-hydroxyphenylacetic acid). In vitro fungal inhibition assays showed that the isolates varied in their ability to inhibit the growth of representative fungal plant pathogens. Fungal inhibition in vitro was superior to that of previously reported Pseudomonas sp. Studies with Fusarium oxysporum forma sp. lycopersici and a susceptible tomato cultivar demonstrated that Pseudomonas putida PPU3.1 was able to significantly reduce wilt disease.     

Regulatory interaction of photosynthetic nitrate utilization and carbon dioxide fixation in the cyanobacterium Anacystis nidulans

The rate of photosynthetic nitrate utilization in Anacystis nidulans is strongly influenced by the availability of carbon dioxide. This dependence can be relieved by inhibiting the metabolism of the ammonium derived from nitrate reduction. Nitrate uptake seems to be modulated through a sensitive regulatory system integrating the photosynthetic metabolism of carbon and nitrogen, with CO₂ fixation products antagonizing the inhibitory effect of ammonium derivatives.     

The steroids and fatty acids of the basidiomycete Scleroderma polyrhizum

The fruit bodies of the Basidiomycete Scleroderma polyrhizum have been shown to contain the steroids ergosta-4,6,8(14) 22-tetraen-3-one and 5α,8α-epidoxyergosta-6,22-dien-3β-ol and also palmitic and oleic acids.