title: 5-Hydroxy-4-oxo-L-norvaline depletes intracellular glutathione: a new modulator of drug resistance.
abstract: To search for compounds that reverse the drug resistance induced by glutathione (GSH), an original screening system to detect intracellular GSH depleters was established. Among 8843 microbes derived from the soil samples tested, the extracts of two Streptomyces species named KS6701 and KS8846, lowered the intracellular GSH level of Saccharomyces cerevisiae 5 x 47. From both the microbes, 5-hydroxy-4-oxo-L-norvaline (HON) was isolated as the active compound. At a concentration of 50-100 micrograms/ml, HON also decreased the GSH/protein level of the human ovarian tumor cell line, 2008/C13*5.25 and reversed its resistance to cisplatin. We also investigated the mechanism of the depletion. HON had little effect on gamma-glutamylcysteine synthetase (gamma-GCS) or glutathione synthetase, but HON decreased the quantity of thiol substances when it was spontaneously reacted with them. This suggested that the GSH depletion by HON occurred through a mechanism different from that of buthionine sulfoximine, a selective gamma-GCS inhibitor.
authors.affiliation: Foods & Pharmaceuticals Research & Development Laboratory, Asahi Breweries Ltd., Midori, Japan. motoyuki.tagashira@asahibeer.co.jp
authors.forename: M
authors.initials: M
authors.lastname: Tagashira
authors.forename: N
authors.initials: N
authors.lastname: Nozato
authors.forename: S
authors.initials: S
authors.lastname: Isonishi
authors.forename: A
authors.initials: A
authors.lastname: Okamoto
authors.forename: K
authors.initials: K
authors.lastname: Ochiai
authors.forename: Y
authors.initials: Y
authors.lastname: Ohtake
mesh_terms: D000622:Aminolevulinic Acid / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000494:pharmacology; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D005260:Female; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D005981:Glutathione Synthase / Q000378:metabolism; D006801:Humans; D010051:Ovarian Neoplasms; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D012988:Soil Microbiology; D013302:Streptomyces / Q000737:chemistry; D014407:Tumor Cells, Cultured
chemical_list: D019328:Buthionine Sulfoximine; C058222:2-amino-5-hydroxy-4-oxopentanoic acid; D000622:Aminolevulinic Acid; D005721:Glutamate-Cysteine Ligase; D005981:Glutathione Synthase; D005978:Glutathione