The organic acids composition of six wild edible mushroom species (Amanita caesarea, Boletus edulis, Gyroporus castaneus, Lactarius deliciosus, Suillus collinitus, and Xerocomus chrysenteron) was determined by an HPLC-UV detector method. The results showed that all of the samples presented a profile composed of at least five organic acids: citric, ketoglutaric, malic, succinic, and fumaric acid...

Malic acid production, degradation, and storage during fruit development have been modelled. The model assumes that malic acid content is determined essentially by the conditions of its storage in the mesocarp cells, and provides a simplified representation of the mechanisms involved in the accumulation of malate in the vacuole and their regulation by thermodynamic constraints. Solving the corr...

Homogenates prepared from bovine heart muscle contain two distinct forms of malic enzyme (malate:NADP+ oxidoreductase (decarboxylating), EC 1.1.1.40), which can be easily separated by chromatography on DEAE-cellulose. A partial purflcation of the two enzymes has been accomplished by means of DEAE-cellulose chromatography, ammonium sulfate fractionation, and chromatography on CMSephadex. The iso...

Enzymes involved in malic acid production via a pathway with 2 carboxylation reactions and in malic acid conversion via total oxidation have been demonstrated in mitochondria of Bryophyllum tubiflorum Harv. Activation of the mitochondria by Tween 40 was necessary to reveal part of the enzyme activities. The temperature behavior of the enzymes has been investigated, revealing optimal activity of...

Phosphoenolpyruvate carboxykinase has been found in significant activities in a number of plants exhibiting Crassulacean acid metabolism. Thirty-five species were surveyed for phosphoenolpyruvate carboxykinase, phosphoenolpyruvate carboxylase, ribulose diphosphate carboxylase, malic enzyme, and malate dehydrogenase (NAD). Plants which showed high activities of malic enzyme contained no detectab...

In Clostridium thermocellum, a thermophilic anaerobic bacterium able to rapidly ferment cellulose to ethanol, pyruvate kinase (EC 2.7.1.40) is absent based on both the genome sequence and enzymatic assays. Instead, a new pathway converting phosphoenolpyruvate to pyruvate via a three-step pathway involving phosphoenolpyruvate carboxykinase, NADH-linked malate dehydrogenase, and NADP-dependent ma...

Previous investigations from this laboratory have revealed that the over-all oxidative capacity of tumor tissues, in general, falls in the range of the less active normal tissues and at a level much lower than normal liver, kidney, heart, or brain (12), while the enzymes of the glycolytic system occur in quantities of the same order of magnitude in all these tissues (5, 6). Since the conclusion...

The regulatory properties of the NAD-dependent malic enzyme from the mitochondria of Ascaris suum have been studied. The malate saturation curve exhibits sigmoidicity and the degree of this sigmoidicity increases as the pH is increased. Fumarate was the only compound tested that stimulated the enzyme activity, whereas oxalacetate was the most powerful inhibitor. Activation by low levels of fuma...

Enzymes in the histologically normal liver of hosts of mammary carcinomas were examined for their responsiveness to endocrine and dietary modulations. Treatments with the developmental stimuli of alanine aminotransferase (glucocorticoids) and of pyruvate kinase (thyroid hormone) which had no effect in control adult rats raised the levels of these enzymes in the tumor-bearing rats. The latter al...

Objectives: Use of certain drugs is the most common aetiology of xerostomia. Systemic sialogogues provide a longer effect than topic ones, but also induce relevant side effects. Topical sialogogues, as malic acid, allow a safe use as they induce no systemic side-effects or pharmacological interactions, being especially interesting in cases of mild hyposalivation and oral dryness, mainly the chr...