Degradation of rutin by Aspergillus flavus. Purification and characterization of rutinase

Aspergillus flavus produces an adaptive glycosidase (rutinase) that hydrolyzes rutin to quercetin and rutinose. Production of rutinase occurs when the mold is grown on the glycosides rutin, hyperosid, and naringin, and on the aglycones quercetin, kaempferol, rhamnetin, 2,4-dihydroxybenzoic acid, and 3,4-dihydroxyphenylacetic acid, but not when grown on glucose, galactose, rhamnose, or rutinose. Rutinase, after partial purification, is relatively stable when stored at −20 °C, and is most stable and most active at pH 5.6. The enzyme is quite specific, hydrolyzing the 5-glucoside of sakuranetin, the 3-rutinoside and 3-galactoside of quercetin, but not the 3-L-rhamnoside nor any of the common glycosides. The hydrolysis of rutin is carried to completion aided by the insolubility of the aglycone quercetin in water.

beta-D-1, 2-Glucanases in fungi

β-D-1,2-Glucans apparently occur rarely in nature, and yet many fungi have the ability to produce a β-1,3-glucanase capable of hydrolyzing them. The β-1,2-glucanases in fungi are adaptive, like the β-1,4-glucanases, and thus differ from the β-1.3- and the β-1,6-glucanases which are constitutive. Enzymatic hydrolysis of the β-1,2-glucan is random, a series of β-1,2-linked oligosaccharides, including sophorose, being formed.

Production of extracellular and total invertase by Candida utilis, Saccharomyces cerevisiae, and other yeasts

Some strains of Candida utilis produce exceptionally large amounts of extracellular and total invertase. Strain Y-900 of C. utilis produces high yields whether the carbon source is sucrose, glucose, maltose, or xylose and still higher yields with lactic acid, glycerol, and ethyl alcohol. Approximately 20 to 30% of the total invertase of C. utilis is extracellular. Strains of Saccharomyces cerevisiae and Saccharomyces carlsbergensis are generally inferior to C. utilis in production of extracellular and total invertase, the difference being accentuated in shaken cultures. The industrial yeasts are generally superior in invertase production to the other yeasts included in the survey.

The effect of exogenous energy sources on the synthesis of beta-galactosidase in resting-cell suspensions of Escherichia coli

Using methyl-1-thio-β-D-galactoside as the inducer, the biosynthesis of β-galactosidase was observed in Escherichia coli B with only endogenous sources of nitrogen and energy available. The addition of glucose, ribose, xylose, or glycerol as exogenous energy sources to nitrogen-deficient media blocked enzyme formation. Preinduction of the resting cells failed to overcome inhibition by the added energy sources. With limited quantities of glucose, ribose, xylose, or glycerol, synthesis of β-galactosidase resumed abruptly and continued at the rate normal for cells in nitrogen-deficient media. Comparison of enzyme activities with oxygen uptake data revealed a reduction in the rate of oxygen uptake at the time enzyme synthesis resumed in media originally containing small amounts of energy sources. This change corresponded to only a fraction of the oxygen required for complete oxidation of one of the exogenous substrates. It is suggested that inhibition by these particular exogenous substrates involves metabolism to a common repressor or interference with an energy-transfer system.