Observations on a strain of Neisseria meningitidis in the presence of glucose and maltose. III. Cell-free extracts and the phosphorolysis of maltose

Partial purification and characterization of alpha-glucosidase from Pseudomonas fluorescens W

The alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) of Pseudomonas fluorescens W was partially purified by (NH4)2SO4 fractionation, Sephadex G-200 and DEAE-cellulose column chromatography. The enzyme showed great specificity for maltose hydrolysis, with very little action against polymeric forms. Sucrose, isomaltose, alpha-methylglucoside, and maltobionic acid were not hydrolyzed. Turanose was a strong competitive inhibitor, and glucose a weaker one. Tris (2-amino-2-hydroxymethylpropan-1:3-diol) inhibited enzyme activity significantly only at alkaline pH. Mercuric, cupric, and silver cations strongly inhibited, and EDTA (ethylenediaminetetraacetate) weakly inhibited the enzyme. The isolated enzyme was rather unstable even at 4 degrees C, and was destroyed by freezing and lyophilization. Inositol and albumin had a slightly protective effect. Sulfhydryl-binding reagents strongly inhibited the enzyme.

Maltose metabolism of Pseudomonas fluorescens

Pseudomonas fluorescens W uses maltose exclusively by hydrolyzing it to glucose via an inducible alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20). No evidence for phosphorolytic cleavage or oxidation to maltobionic acid was found in this organism. The alpha-glucosidase was totally intracellular and was most active at pH of 7.0. Induction occurred when cells were incubated with maltotriose or maltose. Induction was rapid and easily detectable within the first 5 min after the addition of the inducer. Glucose and its derivatives did not repress induction. Cells growing on DL-alanine or succinate plus maltose exhibited lower levels of alpha-glucosidase than those grown on maltose alone or maltose plus glucose. Induction required both messenger ribonucleic acid and protein synthesis.

The metabolism of circulating maltose in man

The utilization of circulating maltose was compared to that of glucose in six normal fasting subjects after intravenous injection of 25 g of either sugar. Blood samples were obtained over a 2 hr period and were assayed for free fatty acids (FFA), insulin, glucose, and total reducing substances. Urine was collected for 2 hr after maltose administration and assayed enzymatically for glucose and maltose. Blood glucose concentrations did not increase after maltose infusion, although a significant rise in total reducing substances was noted, indicating the presence of this disaccharide in the blood. Less than 3% of the administered maltose was excreted in the urine either as maltose or glucose. Initially, there was a fourfold increase in serum insulin concentration after glucose and a threefold increase after maltose infusion. Therefore, serum insulin concentrations gradually declined in a similar manner for both sugars. The plasma FFA at 15 min decreased 371 uEq/liter after glucose and 338 uEq/liter after maltose infusion. In other studies, 10 g maltose containing 5 muCi maltose-U-(14)C were injected into five human subjects and expired CO(2) collected for 6 hr. Maximal (14)CO(2) specific activity was noted at 170 min and a mean of 61.1% of the injected radioactivity was recovered as (14)CO(2). Less than 8% of the injected (14)C was excreted in the urine. These results indicate that maltose administered intravenously has similar metabolic effects when compared to glucose, and may be efficiently utilized as a carbohydrate substrate. The oxidation of intravenously administered maltose-U(14)C to (14)CO(2) demonstrates that circulating maltose is readily metabolized. A solution of maltose could provide twice the mass of sugar (and of calories) per milliliter as an equimolar solution of glucose. Parenterally administered maltose may be of clinical value and should be further studied.

Relationship between sulfadiazine resistance and the failure to ferment maltose in Neisseria meningitidis

The genetic marker for sulfadiazine resistance was transferred by means of purified deoxyribonucleic acid from sulfadiazine-resistant Neisseria meningitidis and N. perflava to a sulfadiazine-sensitive strain of N. meningitidis. Over 80% of the isolates from these experiments, selected on the basis of sulfadiazine resistance, failed to produce acid from maltose. The same proportion of naturally occurring isolates that are sulfadiazine-resistant failed to ferment maltose. The enzymatic block in 17 isolates tested was the loss of maltose permease activity; in two cases, maltose phosphorylase activity was lost also. The permease was present in these cells, however, and could be activated by the addition of sulfadiazine. The results obtained support the hypothesis that these organisms, in becoming resistant to sulfadiazine, have undergone a single mutation.