Biomedical subjects

R Bonaly

Publications and source records attributed to R Bonaly.

At least 55 records · Page 3Linked to original sources

PubMed1977

[Characterization of lipase activity in a yeast of the genus Rhodotorula (Rh. rubra)].

Lipase activity of whole cells of Rh. rubra has been localized in a particular fraction rich in walls and in isolated cell walls. The enzyme activity has been determinated with olive oil and the triglyceride fraction of olive oil as substrats. Gas chromatography of fatty acids and triglycerides isolated after enzyme hydrolysis shows that the action of Rh. rubra is not only limited to a simple hydrolysis of the substrate. The triglyceridase activity level is dependent of the phosphate content of the culture medium.

Cell Wall↗

PubMed1977

[Chemical composition and degradation of the cells walls of a wild-type and of a white mutant of the mushroom Drechslera sorokiniana].

The cell walls of the fungus Drechslera sorokiniana and an albino mutant have been studied to determine if disappearance of pigment also involves an important modification of the chemical structure. The albino mutant has lost, besides the pigment, pentose, xylose, and part of galactose and mannose. The protein contents as well as those of hexosamine and chitin are not modified. After treatments of the walls with 2 M NaOH-0.5 M H2SO4 and with ethylenediamine identical compounds are isolated from the two walls; however, cell walls of the mutant are more easily and more extensively degraded than those of the wild type. This difference in resistance is not only due to the presence of pigment but also to a different architectural structure of the two cell walls.

Amino Acids↗

PubMed1976

[Studies on the cell wall of yeast of the genus Rhodotorula. X. Isolation and purification of cell-wall glycoproteins from Rhodotorula rubra (author's transl)].

Following ethylene diamine treatment of the cell wall of Rhodotorula rubra, a water soluble fraction has been isolated. This fraction can be resolved into three glycoproteins and one protein. The major part is a glycoprotein, purified to homogeneity which has a molecular weight of 64 000. The glyco-part of this protein contains mannose, glucose and one residue of glucosamine. After pronase treatment, the presence of an ""Asparaginyl-N-acetylglucosamine" linkage is established by the existence of one aspartic acid residue and one glucosamine residue. After permethylation, the initial data give some evidence that the branching points in the molecule were the carbon atoms 3 and (or) 6 of the mannose moiety and that some glucose moieties are bound to the non-reducing terminal end.

Acetylglucosamine↗

PubMed1976

[Study of the Rhodotorula rubra cell wall. VII Influence of chloramphenicol on its morphology and phosphatase activity (author's transl)].

Rh. rubra grown in the presence of chloramphenicol (500 mug/ml of medium) displayed morphological and biological changes, including formation of aberrant mitochondria with altered cristae, increase of the ratio fundamental element/mucilaginous sheath and electron-transparent regions in the cell walls. After treatment of the yeast with trypsin or beta-glucanase complex, acid and alkaline phosphatases remained localised within the cell wall, but the effect of the degradative enzymes on the activity of the phosphatses differed in cells grown in the presence of chloramphenicol and those grown without the antibiotic. The data suggest that chloramphenicol induced either structural fragility or increased permeability of the cell walls.

Acid Phosphatase↗

PubMed1976

[Chemical and enzymatic degradation of Helminthosporium spiciferum cell walls. Protective role of pigments].

Cell walls of the fungus Helminthosporium spiciferum, prepared by mechanical grinding of the cells, were treated chemically and with helicase. The purified cell walls and the fractions were analyzed chemically and micromorphologically to localize the major cell-wall constituents and to determine the protective role of the pigments against degradative processes. The encrusting of the external area by the pigments associated with chitin formation leads to an increased resistance of this cell-wall area against the degradative processes.

Amino Acids↗

PubMed1975

[Study of the cell walls of yeasts Rhodotorula. VI'nfluence of 2-hydroxybiphenyl on phosphatase activities of Rh. rubra (author's transl)].

The inhibition of acid phosphatase activity observed after culture of Rh. rubra in phosphate rich mediums is raised by the culture of this yeast in presence of 2-hydroxybiphenyl (OHph2). The cell wall alkaline phosphatase activity was inhibited by this derivative; When cultivated with OHph2 an intra and a more extracellular acid phosphatase activity appeared. The comparative studies of the two extracellular acid phosphatases secreted in the medium with or without the OHph2 show they have similar characteristics. They are eluated at the same time from Sephadex G-200, DEAE- and CM-cellulose columns, and have the same Km. They are both glycoproteins, with the sugars forming the polyose fragment identical, but the enzyme secreted in the medium containing the OHph2 contains less sugar than the one secreted in the medium without OHph2. The appearance of this acid phosphatase activity was attributed to the alteration of the membrane glycosylating systems or to the important ultra structure modifications of the cell wall of Rh. rubra when this yeast is cultivated with OHph2.

Acid Phosphatase↗

PubMed1975

[Study of the cell walls of yeasts Rhodotorulamv'nfluence of the conditions of culture on the phosphatases of Rh; rubra (author's transl)].

1. Acid and alkaline phosphatase activities have been characterized on intact yeast cells and isolated cell walls Rh. rubra. These activities are sensitive to inhibition by orthophosphate. 2. The mechanical disruption does not increase the acid phosphatase activity and almost the entire activity is in the particular fraction. Its response to physicochemical factors is uniform, whatever the state of the preparation. It seemed to be entirely localized in the cell wall. The mechanical disruption of Rh. rubra yeast cells provokes only a small increase in alkaline phosphatase activity. Almost all the activity is in the particular fractions after centrifuging. The response to the physicochemical factors studied differs according to the state of the preparation. This alkaline phosphatase activity is for the most part cell wall localized, but seems also to be located in the periplasmic space or inside the plasmic membrane of Rh. rubra. 3. Trypsine or "beta-glucanase complex" treatments of the yeast cells eliminate much of peptidic and glucidic compounds and provoke a more important increase of the phosphatase activities of yeasts cultivated in rich phosphate media than that obtained after treatments of yeast cultivated in poor phosphate medium. These treatments which affect only the superficial structures of the cell envelope and do not touch the enzymic molecule (the phosphatase Km values are unchanged after treatments, and Ki values are the same before and after treatments) are favourable to a masking of the cell wall phosphatases by culture of Rh. rubra with high concentrations of phosphate. This phenomenon is corroborated by electron microscopy studies.

Acid Phosphatase↗

PubMed1975

[Effect of ethylene diamine on cell wall of three yeasts of the genus Rhodotorula].

The treatment of ethylene diamine of Rhodotorula yeast cells does not alter the fibrillar structure of their wall basic frame. Dissolved substances constitute the external mucilaginous layer and elements intimately incrusted in the wall.

Cell Wall↗

PubMed1973