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B P Yip

Publications and source records attributed to B P Yip.

5 recordsLinked to original sources
PubMed1979

Evidence for mitochondrial localization of the hormone-responsive pool of Ca2+ in isolated hepatocytes.

Conditions are described that allow chlortetracycline, a fluorescent probe of membrane-associated Ca2+, to monitor the content of the major exchangeable pool of intracellular Ca2+ present in the isolated rat hepatocyte. Chlortetracycline fluorescence is decreased in cells whose Ca2+ content is diminished by treatment either with carbonylcyanide-m-chlorophenylhydrazone or with ionophore A23187. Norepinephrine releases Ca2+ from this exchangeable pool and decreases both the fluorescence signal and its subsequent response to A23187. Previous suggestions that chlortetracycline fluorescence is localized in the mitochondria of liver and other cells is supported by comparison of the fluorescence that follows the addition of chlortetracycline to intact hepatocytes and to isolated hepatic microsomes and mitochondria. Identification of the hormone-responsive pool of Ca2+ with the mitochondria is strengthened by comparison of the total calcium content of mitochondria isolated from control and hormone-treated animals. The uptake and release of Ca2+ in control and hormone-treated hepatocytes rendered permeable by treatment with digitonin is also consistent with this interpretation.

Animals↗
PubMed1977

Effect of CrATP on the association of the reacting forms of yeast hexokinase.

Reacting enzyme sedimentation studies have been performed with yeast hexokinase isozymes A and B in the presence and absence of chromium ATP at pH 6.75. Preincubation of either isozyme with CrATP causes a shift in the monomer-dimer equilibrium toward the monomeric form. The results are consistent with the observed increase in inhibition caused by CrATP (Danenberg, K.D., and Cleland, W.W. (1975) Biochemistry 14, 28-39) being due to a conformational change in the protein which causes a decrease in the association constant for the monomer.

Adenosine Triphosphate↗
PubMed1977

The catalytic activity of monomeric yeast hexokinase A.

It has been suggested [Williams, D.C. & Jones, J.G. (1976) Biochem. J. 155, 661-667] that monomeric hexokinase isoenzyme A is not catalytically active. We here present data from reacting-enzyme sedimentation, dissociation experiments and from previous studies which are consistent with the monomeric form possessing catalytic activity.

Catalysis↗
PubMed1976

Interaction of tetraiodofluorescein with yeast hexokinase.

The dye tetraiodofluorescein (TIF) was found to be an effective inhibitor of yeast hexokinase. It is a competitive inhibitor relative to MgATP2- and a noncompetitive inhibitor of glucose binding, a kinetic pattern consistent with the previously proposed random kinetic mechanism. TIF interacts directly with the native dimeric protein to give a difference spectrum with a maximum at 543 nm. Monomeric protein (produced by addition of 0.6 M NaCl) interacts with TIF to give a slightly altered difference spectrum, with the gammamax at 545 nm. The difference spectrum of the dimeric form is not perturbed by the addition of substrates but the absorbance with the monomer is lowered by MgATP2-. The Kd for MgATP2- was estimated to be 7 nM for monomeric hexokinase. These results suggest that results of previous binding studies with hexokinase at high concentrations which have been interpreted as being at variance with kinetic studies are due likely to different conformations of the protein under different experimental conditions.

Adenosine Triphosphate↗