Ranwel Caputto

Activation of deoxycholate solubilized adenosine triphosphatase by ganglioside and asialoganglioside preparations

Abstract ATPase was prepared from brain microsomes by solubilization with sodium deoxycholate and fractionated at different concentrations of ammonium sulfate. The Mg 2+ -ATPase was activated by total brain gangliosides, disialoganglioside, monosialo — ganglioside, hematoside, total brain gangliosides obtained from a patient with Tay-Sachs disease and asialoganglioside. The effect was smaller on Ca 2+ -ATPase and negligible on (Na + + K + )-ATPase. Lactosyl-ceramide, glucosyl-ceramide, galactosyl-ceramide, ceramide and sialyl-lactose failed to produce activation.

Studies on the structure of neuramin-lactose sulfate

1. n1. Chemical and enzymological studies on neuramin-lactose sulfate have provided supporting evidence for the proposed structure: O-α-D-N-acetylneuraminyl-(2→3)-O-β-D-galactopyranosyl6-O-sulfate-(1→4)-D-glucopyranose. n n2. n2. The enzymological studies showed that neuramin-lactose sulfate is hydrolyzed by neuraminidase (EC 3.2.1.18) and that the lactose sulfate moiety of the molecule is resistant to the action of β-galactosidase (EC 3.2.1.23). n n3. n3. The chemical studies showed that during periodate oxidation of neuramin-lactose sulfate, the galactosyl moiety was protected, while in the case of lactose sulfate it underwent complete oxidation. n n4. n4. Synthetic D-galactose 6-O-sulfate and the galactose sulfate isolated from neuramin-lactose sulfate were found to be identical by paper chromatography, ionophoresis, infrared spectra and lack of formaldehyde production during periodate oxidation.

The interrelationship between gulonolactone oxidase and the process of lipid peroxidation.

In 1958 our group reported that the synthesis of ascorbic acid by liver homogenates obtained from animals deprived of vitamin E is impaired when glucuronic acid is used as a starting substrate. The impairment was subsequently found to be due to the inhibition of the microsomal enzyme, gulonolactone oxidase.* The reduction of glucuronate to gulonate or the formation of gulonolactone from gulonate are normal or perhaps slightly increased.

Incorporation of [14C]glucose into lactose and neuramin-lactose by rat mammary glands

Abstract Incubation of rat-mammary-gland slices in a physiological solution containing [ 14 C]glucose disclosed incorporation of radioactivity into both lactose and neuraminlactose. After 1 min incubation the labeling was restricted to the glucose moiety of these molecules while administering the glucose in vivo resulted in labeling of all components of these molecules after 3 h. The specific activities of free lactose and lactose from neuramin-lactose are of similar order of magnitude in all experiments and, although these findings are compatible with the currently known biosynthetic pathways of these substances, the possibility of an alternate pathway involving the action of neuraminidase is suggested in connection with the rapid equilibration of the specific activities of these substances.

Metabolic properties of quinidine; effects of quinidine sulfate on anaerobic carbohydrate metabolism of rat diaphragm.

Summary 1. Quinidine sulfate at a concentration of 1 × 10-3 M strongly inhibits the uptake of glucose and fructose by intact rat diaphragm under anaerobic conditions. 2. Quinidine is without effect on endogenous anaerobic lactic acid production by rat diaphragm. 3. Glucose at a concentration of 1 mg/ml or 4 mg/ml markedly stimulates anaerobic glycolysis while fructose at a concentration of 5 mg/ml produces only a slight stimulation. 4. Stimulation of glycolysis by glucose or fructose is abolished by 1 × 10-3 M quinidine and partially inhibited by 5 × 10-4 M quinidine. 5. It is suggested that quinidine inhibits glucose or fructose uptake prior to the step at which these sugars and glycogen share a common metabolic pathway.

Creatine-phosphate utilization by muscle extracts of rabbits on vit. E-deficient diets.

Summary A method for determination of the transfer of phosphate from creatine-phosphate to the hexosemonophosphates is described. It has been found that this transference is decreased in the muscle of rabbits fed tocopherol-deficient diets at a time when phosphoglucomutase activity and glycolysis are normal. The decrease in transference is not corrected by addition of ATP. ATP added at concentrations above 0.004 M inhibits phosphoglucomutase.