Biomaterial Database

A role for sterols in the porphyrin mediated photosensitization of yeast. 1989

W M Casey, and L W Parks

The yeast Saccharomyces cerevisiae was used as a model system to determine the role of sterols in the porphyrin mediated photosensitization of yeast. A sterol auxotroph, RD5-R, was grown on sterols with different levels of unsaturation and assayed for photosensitivity in the presence of either protoporphyrin IX or hematoporphyrin (both at 100 micrograms/ml). Cells grown on the completely saturated sterol (stanol), cholestanol, were substantially more resistant to the photosensizing effects of the porphyrin. We hypothesize that this resistance arises from the inability of the porphyrin to mediate the oxidation of the membrane sterol. Our results indicate that photodegradation of the native yeast sterol, ergosterol, can account for substantial losses of cell viability.

UI	MeSH Term	Description	Entries
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D010777	Photochemistry	A branch of physical chemistry which studies chemical reactions, isomerization and physical behavior that may occur under the influence of visible and/or ultraviolet light.	Photochemistries
D011166	Porphyrins	A group of compounds containing the porphin structure, four pyrrole rings connected by methine bridges in a cyclic configuration to which a variety of side chains are attached. The nature of the side chain is indicated by a prefix, as uroporphyrin, hematoporphyrin, etc. The porphyrins, in combination with iron, form the heme component in biologically significant compounds such as hemoglobin and myoglobin.	Porphyrin
D012441	Saccharomyces cerevisiae	A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.	Baker's Yeast,Brewer's Yeast,Candida robusta,S. cerevisiae,Saccharomyces capensis,Saccharomyces italicus,Saccharomyces oviformis,Saccharomyces uvarum var. melibiosus,Yeast, Baker's,Yeast, Brewer's,Baker Yeast,S cerevisiae,Baker's Yeasts,Yeast, Baker
D013261	Sterols	Steroids with a hydroxyl group at C-3 and most of the skeleton of cholestane. Additional carbon atoms may be present in the side chain. (IUPAC Steroid Nomenclature, 1987)	Sterol