Pyruvate carboxylase from rat liver: Catalytic properties in the absence, and at low concentrations, of acetyl-CoA

1972 ◽  
Vol 48 (1) ◽  
pp. 85-93 ◽  
Author(s):  
Michael C. Scrutton ◽  
M.Dawn White
Keyword(s):  
Rat Liver ◽  
Pyruvate Carboxylase ◽  
Catalytic Properties ◽  
Acetyl Coa ◽  
Low Concentrations

scholarly journals Factors that influence the translocation of the N-carboxybiotin moiety between the two sub-sites of pyruvate carboxylase

1981 ◽  
Vol 199 (3) ◽  
pp. 603-609 ◽  
Author(s):  
G J Goodall ◽  
G S Baldwin ◽  
J C Wallace ◽  
D B Keech
Keyword(s):  
Dissociation Constant ◽  
Carboxy Group ◽  
Active Site ◽  
Pyruvate Carboxylase ◽  
Alternative Substrate ◽  
Acetyl Coa ◽  
Low Concentrations ◽  
Acid Substrate ◽  
Allosteric Activator ◽  
Rate Of Movement

The active site of pyruvate carboxylase, like those of all biotin-dependent carboxylases, is believed to consist of two spatially distinct sub-sites with biotin acting as a mobile carboxy-group carrier oscillating between the two sub-sites. Some of the factors that influence the location and rate of movement of the N-carboxybiotin were studied. The rate of carboxylation of the alternative substrate, 2-oxobutyrate, was measured at 0 degrees C in an assay system where the isolated enzyme--[14C]carboxybiotin was the carboxy-group donor. The results are consistent with the hypothesis that the location of the carboxybiotin in the active site is determined by the presence of Mg2+, acetyl-CoA and the oxo acid substrate. The presence of Mg2+ favours the holding of the complex at the first sub-site, whereas alpha-oxo acids induce the complex to move to the second sub-site. At low concentrations pyruvate induces this movement but does not efficiently act as a carboxy-group acceptor; hydroxypyruvate, glyoxylate and oxamate, though not carboxylated, still induce the movement. The allosteric activator acetyl-CoA exerts only a slight stimulation on the rate of translocation to the second sub-site, and this stimulation arises from an increase in the dissociation constant for Mg2+.

scholarly journals Rat Liver Pyruvate Carboxylase

1971 ◽  
Vol 246 (11) ◽  
pp. 3569-3578 ◽  
Author(s):  
W.R. McClure ◽  
Henry A. Lardy ◽  
Helmut P. Kneifel
Keyword(s):  
Rat Liver ◽  
Pyruvate Carboxylase

scholarly journals Inhibition of rat liver acetyl CoA carboxylase by chloride

1980 ◽  
Vol 21 (4) ◽  
pp. 488-491
Author(s):  
J B Allred ◽  
K L Roehrig
Keyword(s):  
Rat Liver ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa

scholarly journals The roles of phospholipase D and a GTP-binding protein in guanosine 5′-[γ-thio]triphosphate-stimulated hydrolysis of phosphatidylcholine in rat liver plasma membranes

1990 ◽  
Vol 272 (3) ◽  
pp. 749-753 ◽  
Author(s):  
K M Hurst ◽  
B P Hughes ◽  
G J Barritt
Keyword(s):  
Rat Liver ◽  
Phospholipase D ◽  
Plasma Membranes ◽  
Regulatory Protein ◽  
Gtp Binding ◽  
Liver Plasma Membranes ◽  
Low Concentrations ◽  
Rat Liver Plasma Membranes ◽  
Triton X ◽  
Hydrolysis Of

1. Guanosine 5′-[gamma-thio]triphosphate (GTP[S]) stimulated by 50% the rate of release of [3H]choline and [3H]phosphorylcholine in rat liver plasma membranes labelled with [3H]choline. About 70% of the radioactivity released in the presence of GTP[S] was [3H]choline and 30% was [3H]phosphorylcholine. 2. The hydrolysis of phosphorylcholine to choline and the conversion of choline to phosphorylcholine did not contribute to the formation of [3H]choline and [3H]phosphorylcholine respectively. 3. The release of [3H]choline from membranes was inhibited by low concentrations of SDS or Triton X-100. Considerably higher concentrations of the detergents were required to inhibit the release of [3H]phosphorylcholine. 4. Guanosine 5′-[beta gamma-imido]triphosphate and guanosine 5′-[alpha beta-methylene]triphosphate, but not adenosine 5′-[gamma-thio]-triphosphate, stimulated [3H]choline release to the same extent as did GTP[S]. The GTP[S]-stimulated [3H]choline release was inhibited by guanosine 5′-[beta-thio]diphosphate, GDP and GTP but not by GMP. 5. It is concluded that, in rat liver plasma membranes, (a) GTP[S]-stimulated hydrolysis of phosphatidylcholine is catalysed predominantly by phospholipase D with some contribution from phospholipase C, and (b) the stimulation of phosphatidylcholine hydrolysis by GTP[s] occurs via a GTP-binding regulatory protein.

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