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At least 973 records · Page 54Linked to original sources
PubMed1963

Distinctive properties of beta-glucosidases and related enzymes derived from a commercial Aspergillus niger cellulase.

Eight highly purified beta-glucosidases from Aspergillus niger were compared enzymatically, chemically, and immunologically. Ultraviolet spectra, pH-activity responses, substrate specificities, thermal stabilities, kinetic changes in the viscosity of substrate, Michaelis-Menten parameters, adsorption characteristics on cellulose, and exclusion characteristics on dextran gels were determined. The data indicate that the several components represent distinctly different enzymes in terms of mode of attack on substrate. The concept of partial denaturation of a single enzyme precursor is unable to explain the heterogeneity observed. Comparison of the effect of pH on hydrolysis of carboxymethylcellulose and cellohexaose suggests that a negative charge center on the substrate has a pronounced inhibitory effect on the enzymes.

Aspergillus↗
PubMed1964

QUANTITATIVE STUDIES ON GLYCOLYTIC ENZYMES IN LACTOBACILLUS PLANTARUM. II. INTRACELLULAR CONCENTRATIONS OF GLYCOLYTIC INTERMEDIATES IN GLUCOSE-METABOLIZING WASHED CELLS.

Mizushima, Shôji (University of Tokyo, Tokyo, Japan), and Kakuo Kitahara. Quantitative studies on glycolytic enzymes in Lactobacillus plantarum. II. Intracellular concentrations of glycolytic intermediates in glucose-metabolizing washed cells. J. Bacteriol. 87:1429-1435. 1964.-The intracellular concentrations of glycolytic intermediates in glucose-metabolizing cells could be estimated by using C(14)-glucose of high specific activity. Separation of each intermediate was accomplished by column chromatography with Dowex 1-X8 (formate) ion-exchange resin. If the intermediates were inseparable, one was converted into another substance separable by chromatography. Almost all the glycolytic intermediates were found to be radioactive, and all of the radioactive substances appearing on the chromatograms were limited to glycolytic intermediates or their related substances. The results clearly show the role of the glycolytic system for lactic acid fermentation in the organism. Among the intermediates, fructose-1,6-diphosphate and 3-phosphoglycerate were found to be present in relatively high concentrations. The reason for the high concentrations of these compounds is discussed.

Carbohydrate Metabolism↗
PubMed1989

Ethanol inhibition of Saccharomyces and Candida enzymes.

Ethanol inhibition of several hydrolases (sucrase, maltase, trehalase, melezitase and cellobiase) has been measured in both highly ethanol-tolerant Saccharomyces strains (R) and in Candida strains less tolerant to ethanol (S). Cells were either grown in the presence of ethanol and the activities of the enzymes measured without preincubation in this alcohol ("in situ" inhibition assay), or the culture was grown in the absence of ethanol and the activities of the enzymes were determined after preincubation and in the presence of this compound ("in vitro" inhibition assay). Ethanol inhibition (Ki values) of sucrase, maltase, trehalase, and melezitase was quite different for these different enzymes in the same strain (R or S), but similar for the same enzyme in different strains (R and S). The Ki values for cellobiase, which is absent from the R strain, were higher when induced than at the basal level and higher in in vitro assays than in in situ assays. This suggests that the inhibition observed in situ is mainly the result of an inhibition of other proteins related to cellobiase (i.e., those involved in its synthesis) but not a direct inactivation of the enzyme by ethanol. Accordingly, when hybrids between Saccharomyces (R) and Candida (S) strains were constructed by protoplast fusion, and cellobiase was measured in the parental Candida strain and some of the hybrids, there was an increase in the Ki values in the in situ assays from 2.25% ethanol in Candida to 5.5% in some of the hybrids.

Candida↗