/sup 31/P NMR saturation-transfer measurements in Saccharomyces cerevisiae: characterization of phosphate exchange reactions by iodoacetate and antimycin A inhibition
/sup 31/P nuclear magnetic resonance (NMR) saturation-transfer (ST) techniques have been used to measure steady-state flows through phosphate-adenosine 5'-triphosphate (ATP) exchange reactions in glucose-grown derepressed yeast. The results have revealed that the reactions catalyzed by glyceraldehyde-3-phosphate dehydrogenase/phosphoglycerate kinase (GAPDH/PGK) and by the mitochondrial ATPase contribute to the observed ST. Contributions from these reactions were evaluated by performing ST studies under various metabolic conditions in the presence and absence of either iodoacetate, a specific inhibitor of GAPDH, or the respiratory chain inhibitor antimycin A. Intracellular phosphate (P/sub i/) longitudinal relaxation times were determined by performing inversion recovery experiments during steady-state ATP/sub lambda/ saturation and were used in combination with ST data to determine P/sub i/ consumption rates. /sup 13/C NMR and O/sub 2/ electrode measurements were also conducted to monitor changes in rates of glucose consumption and O/sub 2/ consumption, respectively, under the various metabolic conditions examined. The results suggest that GAPDH/PGK-catalyzed P/sub i/-ATP exchange is responsible for antimycin-resistant saturation transfer observed in anaerobic and aerobic glucose-fed yeast. Kinetics through GAPDH/PGK were found to depend on metabolic conditions. The coupled system appears to operate in a unidirectional manner during anaerobic glucose metabolism and bidirectionally when the cells are respiring on exogenously supplied ethanol. Additionally, mitochondrial ATPase activity appears to be responsible for the transfer observed in iodoacetate-treated aerobic cells supplied with either glucose or ethanol, with synthesis of ATP occurring unidirectionally.
- Research Organization:
- Yale Univ., New Haven, CT
- OSTI ID:
- 5435772
- Journal Information:
- Biochemistry; (United States), Vol. 26:23
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ANTIMETABOLITES
BIOLOGICAL EFFECTS
ANTIMYCIN
SACCHAROMYCES CEREVISIAE
METABOLISM
NUCLEAR MAGNETIC RESONANCE
ACETATES
ATP
ATP-ASE
BIOCHEMICAL REACTION KINETICS
CARBON 13
GLUCOSE
OVERHAUSER EFFECT
OXYGEN
PHOSPHORUS 31
PHOSPHOTRANSFERASES
ACID ANHYDRASES
ALDEHYDES
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
CARBOHYDRATES
CARBON ISOTOPES
CARBOXYLIC ACID SALTS
DRUGS
ELEMENTS
ENZYMES
EVEN-ODD NUCLEI
FUNGI
HEXOSES
HYDROLASES
ISOTOPES
KINETICS
LIGHT NUCLEI
MAGNETIC RESONANCE
MICROORGANISMS
MONOSACCHARIDES
NONMETALS
NUCLEI
NUCLEOTIDES
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PHOSPHOHYDROLASES
PHOSPHORUS ISOTOPES
PHOSPHORUS-GROUP TRANSFERASES
PLANTS
REACTION KINETICS
RESONANCE
SACCHARIDES
SACCHAROMYCES
STABLE ISOTOPES
TRANSFERASES
YEASTS
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