diphenylhexatriene and alpha-glycerophosphoric-acid

FAD-linked L-glycerol-3-phosphate dehydrogenase purified from liver mitochondria of hyperthyroid rats was incorporated into unilamellar phospholipid liposomes. The incorporation influenced both Vmax,app and Km,app values of the enzyme for its substrate, L-glycerol 3-phosphate. The Km,app for the electron acceptor remained unchanged with a simultaneous slight enhancement of the corresponding Vmax,app value. The steady-state fluorescence anisotropies of the fluorescein isothiocyanate and trimethylammoniumdiphenylhexatriene labels were affected by sodium oleate and calcium ions in the case of both solubilized and liposome-incorporated L-glycerol-3-phosphate dehydrogenase. These results indicate that calcium ions cause a significant alteration of the enzyme conformation. Sodium oleate (used as a model of free fatty acids), besides its direct action on the enzyme itself, affects the enzyme indirectly as well, via alteration of the physical properties of the membrane.

Topics: Animals; Calcium; Cardiolipins; Diphenylhexatriene; Fluorescein-5-isothiocyanate; Fluoresceins; Fluorescent Dyes; Glycerolphosphate Dehydrogenase; Glycerophosphates; Hyperthyroidism; Kinetics; Liposomes; Male; Mitochondria, Liver; Oleic Acid; Oleic Acids; Phospholipids; Protein Conformation; Rats; Spectrometry, Fluorescence; Thiocyanates

The inhibition of glycerol 3-phosphate oxidation by oleic acid correlates with changes in membrane microviscosity monitored by the steady-state fluorescence anisotropy of DPH. The dynamic measurements indicate that the changes of both the limiting anisotropy and rotational relaxation time occur in a concentration range where the enzyme activity is strongly inhibited.

Topics: Adipose Tissue, Brown; Animals; Cricetinae; Diphenylhexatriene; Fluorescence Polarization; Glycerophosphates; Intracellular Membranes; Lipid Bilayers; Mitochondria; Oleic Acid; Oleic Acids; Oxidation-Reduction; Viscosity