Main polyol dehydrogenase of Gluconobacter suboxydans IFO 3255, membrane-bound D-sorbitol dehydrogenase, that needs product of upstream gene, sldB, for activity. (17/79)

The D-sorbitol dehydrogenase gene, sldA, and an upstream gene, sldB, encoding a hydrophobic polypeptide, SldB, of Gluconobacter suboxydans IFO 3255 were disrupted in a check of their biological functions. The bacterial cells with the sldA gene disrupted did not produce L-sorbose by oxidation of D-sorbitol in resting-cell reactions at pHs 4.5 and 7.0, indicating that the dehydrogenase was the main D-sorbitol-oxidizing enzyme in this bacterium. The cells did not produce D-fructose from D-mannitol or dihydroxyacetone from glycerol. The disruption of the sldB gene resulted in undetectable oxidation of D-sorbitol, D-mannitol, or glycerol, although the cells produced the dehydrogenase. The cells with the sldB gene disrupted produced more of what might be signal-unprocessed SldA than the wild-type cells did. SldB may be a chaperone-like component that assists signal processing and folding of the SldA polypeptide to form active D-sorbitol dehydrogenase.  (+info)

Characterization of the glucose transport systems in Neurospora crassa sl. (18/79)

Neurospora crassa sl, a mutant that lacks a rigid cell wall, exhibits transport systems for glucose similar to those of wild-type strain 1A. When the orgnism is grown in a medium containing 50 mM glucose as the carbon source, glucose is transported primarily by a glucose-facilitated diffusion system (GluI). When it is grown in a medium with little or no glucose present, a glucose active transport system (Glu II) is expressed. Both of these systems are similar kinetically to those in the wild type. Significant differences do exist between strains sl and 1A with respect to genetic regulation of the glucose active transport system.  (+info)

The action of the excretory apparatus of Calliphora vomitoria in handling injected sugar solution. (19/79)

Recent evidence suggests that the isolated Malpighian tubules of Calliphora possess mechanisms which restrict the loss of glucose and trehalose from the insect. This report establishes that the intact, diuresing fly does not excrete glucose or trehalose when solutions of these sugars are injected. When solutions of non-metabolized sugars such as sorbose and xylose are injected into the fly, these sugars are rapidly excreted. High concentrations of sorbose and xylose are found in the urine, suggesting that rapid reabsorption of fluid occurs in the excretory apparatus even during the diuresis which the injections provoke. However, injected sucrose is apparently not excreted in large amounts and it is possible that the Malpighian tubules when functioning in vivo are impermeable to disaccharides.  (+info)

Glucose uptake in germinating Aspergillus nidulans conidia: involvement of the creA and sorA genes. (20/79)

D-Glucose uptake in germinating wild-type Aspergillus nidulans conidia is an energy-requiring process mediated by at least two transport systems of differing affinities for glucose: a low-affinity system (K(m) approximately 1.4 mM) and a high-affinity system (K(m) approximately 16 micro M). The low-affinity system is inducible by glucose; the high-affinity system is subject to glucose repression effected by the carbon catabolite repressor CreA and is absent in sorA3 mutant conidia, which exhibit resistance to L-sorbose toxicity. An intermediate-affinity system (K(m) approximately 400 micro M) is present in sorA3 conidia germinating in derepressing conditions. creA derepressed mutants show enhanced sensitivity to L-sorbose. The high-affinity uptake system appears to be responsible for the uptake of this toxic sugar.  (+info)

Lecithin requirement for the sporulation process in Neurospora crassa. (21/79)

Reversible inhibition of conidiogenesis occurred when lecithin was depleted from Neurospora membranes by choline starvation.  (+info)

Mechanism of glucose transport across the yeast cell membrane. (22/79)

Cirillo, Vincent P. (Seton Hall College of Medicine and Dentistry, Jersey City, N.J.). Mechanism of glucose transport across the yeast cell membrane. J. Bacteriol. 84:485-491. 1962.-The kinetics of d-glucose and l-sorbose transport was studied in Saccharomyces cerevisiae inhibited with iodoacetic acid under nitrogen to prevent glucose metabolism. d-Glucose was found to compete with l-sorbose for a common membrane transport system with an apparent affinity greater than 25 times that of sorbose. A comparison of the net rate of glucose and sorbose transport at 50 and 500 mm external concentration showed that glucose transport is greater than that of sorbose from the lower concentration, but sorbose transport is greater than glucose at the higher concentration. This reversal of transport rate of two sugars with markedly different affinities is predicted by the membrane carrier theory. A further prediction of carrier theory was confirmed by the demonstration that the rate of glucose transport into fructose-loaded cells is greater than into unloaded cells.  (+info)

Sugar transport by Saccharomyces cerevisiae protoplasts. (23/79)

Cirillo, Vincent P. (Seton Hall College of Medicine and Dentistry, Jersey City, N.J.). Sugar transport by Saccharomyces cerevisiae protoplasts. J. Bacteriol. 84:1251-1253. 1962.-By the use of Saccharomyces cerevisiae protoplasts, the l-sorbose transport mechanism has been associated with the protoplast membrane rather than the cell wall. The osmotic fragility of protoplasts in l-sorbose solutions shows that the transported sugar remains osmotically active.  (+info)

SUGAR TRANSPORT IN A PSYCHROPHILIC YEAST. (24/79)

Cirillo, Vincent P. (Seton Hall College of Medicine and Dentistry, Jersey City, N.J.), Peter O. Wilkins, and Joseph Anton. Sugar transport in a psychrophilic yeast. J. Bacteriol. 86:1259-1264. 1963.-The mechanism and temperature characteristic for sugar transport were compared in a psychrophilic and a mesophilic yeast. Between 0 and 10 C, glucose utilization, glucosamine accumulation, and sorbose transport showed a very high temperature characteristic in the mesophile (mu = 50,000) compared with the psychrophile (mu = 12,000). Hexokinase activity in cell-free extracts from both yeasts, however, showed the same low temperature characteristic (mu = 15,000). Although the temperature characteristic for sugar transport was markedly different for the mesophile and the psychrophile, sugar transport in both yeasts met the criteria for carrier-mediated facilitated diffusion.  (+info)