scholarly journals Effects of adenosine phosphates and nicotinamide nucleotides on pyruvate carboxylase from baker's yeast

1969 ◽  
Vol 112 (5) ◽  
pp. 755-762 ◽  
Author(s):  
J. J. Cazzulo ◽  
A. O. M. Stoppani
Keyword(s):  
Enzyme Activity ◽  
Pyruvate Carboxylase ◽  
Physiological Role ◽  
Inhibitory Effect ◽  
Baker’S Yeast ◽  
Baker's Yeast ◽  
Acetyl Coa ◽  
Competitive Inhibitors ◽  
Adenosine Phosphates ◽  
Regulation Of Enzyme Activity

1. Pyruvate carboxylase from baker's yeast is inhibited by ADP, AMP and adenosine at pH8·0 in the presence of magnesium chloride concentrations equal to or higher than the ATP concentration. The adenine moiety is essential for the inhibitory effect. 2. In the absence of acetyl-CoA (an allosteric activator) ADP, AMP and adenosine are competitive inhibitors with respect to ATP. In the presence of acetyl-CoA, besides the effect with respect to ATP, AMP competes with acetyl-CoA, whereas ADP and adenosine are non-competitive inhibitors with respect to the activator. 3. Pyruvate carboxylase is inhibited by NADH. The inhibition is competitive with respect to acetyl-CoA and specific with respect to NADH, since NAD+, NADP+ and NADPH do not affect the enzyme activity. In the absence of acetyl-CoA, NAD+, NADH, NADP+ and NADPH do not inhibit pyruvate carboxylase. 4. Pyruvate carboxylase is inhibited by ADP, AMP and NADH at pH6·5, in the presence of 12mm-Mg2+, 0·75mm-Mn2+ and 0·5mm-ATP, medium conditions similar to those existing inside the yeast cell. The ADP and NADH effects are consistent with a regulation of enzyme activity by the intracellular [ATP]/[ADP] ratio and secondarily by NADH concentration. These mechanisms would supplement the already known control of yeast pyruvate carboxylase by acetyl-CoA and l-aspartate. Inhibition by AMP is less marked and its physiological role is perhaps limited.

scholarly journals The unfolding and refolding of glutamate dehydrogenases from bovine liver, baker's yeast and Clostridium symbosium

1988 ◽  
Vol 251 (1) ◽  
pp. 135-139 ◽  
Author(s):  
S M West ◽  
N C Price
Keyword(s):  
Enzyme Activity ◽  
Light Scattering ◽  
Liver Enzyme ◽  
Structural Changes ◽  
Bovine Liver ◽  
Baker’S Yeast ◽  
Baker's Yeast ◽  
Guanidinium Chloride ◽  
Reversible Loss ◽  
Parallel Behaviour

The unfolding behaviour of the hexameric glutamate dehydrogenases from bovine liver, Clostridium symbosium and baker's yeast in solutions of guanidinium chloride (GdnHCl) was studied. Changes in Mr studied by light-scattering indicate that, in each case, the hexamer dissociates to form trimers, which then dissociate to monomers at higher concentrations of GdnHCl. Dissociation to trimers is accompanied by a reversible loss of enzyme activity, but no gross structural changes can be detected by fluorescence or c.d. Dissociation to monomers is accompanied by large structural changes, and the loss of activity cannot be reversed by dilution. The parallel behaviour of all three enzymes shows that the previously noted inability of the isolated subunits of the bovine liver enzyme to refold [Bell & Bell (1984) Biochem. J. 217, 327-330] is not a result of any modification of the enzyme as a result of import into mitochondria, since the C. symbosium and baker's-yeast enzymes do not undergo any such post-translational translocation.

Phenylalanine Analogues: Potent Inhibitors of Phenylalanine Ammonia-Lyase Are Weak Inhibitors of Phenylalanine-tRNA Synthetases

1994 ◽  
Vol 49 (11-12) ◽  
pp. 781-790 ◽  
Author(s):  
Gerhard Leubner Metzger ◽  
Nikolaus Amrhein
Keyword(s):  
Wheat Germ ◽  
Phenylalanine Ammonia Lyase ◽  
Inhibitory Effect ◽  
Baker’S Yeast ◽  
Baker's Yeast ◽  
Exchange Reactions ◽  
Trna Synthetases ◽  
Different Sources

(1-Amino-2-phenylethyl)phosphonic acid (APEP), (1-amino-2-phenylethyl)phosphonous acid (APEPi), α-aminooxy-β-phenylpropionic acid (AOPP) and several other phenylalanine analogues are potent inhibitors of (S)-phenylalanine ammonia-lyase (PAL) in vitro and in vivo. The ability of these compounds to inhibit (S)-phenylalanine-tRNA synthetases (PRSs) from wheat germ, soybean, and baker’s yeast has been investigated and compared to the inhibition of PAL. APEP and APEPi were found to inhibit the tRNAphe-aminoacylation reactions catalyzed by the three PRSs studied in vitro in a competitive manner with respect to (5)-phenylalanine. (R)-APEP inhibits the PRSs with apparent Ki values of 144 μᴍ for wheat germ (app. Km for (S)-phe 5.2 μᴍ) , 130 μᴍ for soybean (app. Km for (S)-phe 0.9 μᴍ) , and 1096 μᴍ for baker’s yeast (app. Km for (S)-phe 5.5 μᴍ ) . The apparent Ki values for (R)-APEPi are 315 μᴍ , 160 μᴍ , and 117 μᴍ , respectively. APEP and APEPi inhibit the ATPpyrophosphate exchange reactions catalyzed by the PRSs from wheat germ and baker’s yeast, but they are not activated and do not serve as substrates in these reactions. AOPP has no affinity to any of the three PRSs, whereas it is a potent inhibitor of PAL. In light of our in vitro results with PRSs from different sources it appears unlikely that the PAL inhibitors we have studied have any significant inhibitory effect on this essential step in protein synthesis in vivo.

scholarly journals Inhibitory Properties of Aqueous Ethanol Extracts of Propolis on Alpha-Glucosidase

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Hongcheng Zhang ◽  
Guangxin Wang ◽  
Trust Beta ◽  
Jie Dong
Keyword(s):  
Aqueous Ethanol ◽  
Competitive Inhibition ◽  
Inhibitory Effect ◽  
Postprandial Hyperglycemia ◽  
Baker’S Yeast ◽  
Baker's Yeast ◽  
Ethanol Extracts ◽  
Alpha Glucosidase ◽  
Mammalian Intestine ◽  
Intestinal Sucrase

The objective of the present study was to evaluate the inhibitory properties of various extracts of propolis on alpha-glucosidase from baker’s yeast and mammalian intestine. Inhibitory activities of aqueous ethanol extracts of propolis were determined by using 4-nitrophenyl-D-glucopyranoside, sucrose and maltose as substrates, and acarbose as a positive reference. All extracts were significantly effective in inhibitingα-glucosidase from baker’s yeast and rat intestinal sucrase in comparison with acarbose (P<0.05). The 75% ethanol extracts of propolis (75% EEP) showed the highest inhibitory effect onα-glucosidase and sucrase and were a noncompetitive inhibition mode. 50% EEP, 95%, EEP and 100% EEP exhibited a mixed inhibition mode, while water extracts of propolis (WEP) and 25% EEP demonstrated a competitive inhibition mode. Furthermore, WEP presented the highest inhibitory activity against maltase. These results suggest that aqueous ethanol extracts of propolis may be used as nutraceuticals for the regulation of postprandial hyperglycemia.

scholarly journals Effects of magnesium, manganese and adenosine triphosphate ions on pyruvate carboxylase from baker's yeast

1969 ◽  
Vol 112 (5) ◽  
pp. 747-754 ◽  
Author(s):  
J. J. Cazzulo ◽  
A. O. M. Stoppani
Keyword(s):  
Yeast Cell ◽  
Magnesium Chloride ◽  
Pyruvate Carboxylase ◽  
Total Concentration ◽  
Enzyme Reaction ◽  
Enzyme Activation ◽  
Baker’S Yeast ◽  
Manganese Chloride ◽  
Baker's Yeast ◽  
Experimental Conditions

1. Pyruvate carboxylase from baker's yeast acts with either MgATP2− or MnATP2− as substrate. The optimum pH for the enzyme reaction is 8·0 with MgATP2− and 7·0 with MnATP2−. 2. When the reaction velocity is plotted against MgATP2− (or MnATP2−) concentration slightly sigmoid curves are obtained, either in the presence or in the absence of acetyl-CoA (an allosteric activator). In the presence of excess of free Mg2+ (or Mn2+) the curves turn into hyperbolae, whereas in the presence of excess of free ATP4− the apparent sigmoidicity of the curves increases. 3. The sigmoidicity of the plots of v against MgATP2− (or MnATP2−) concentration can be explained by the inhibitory effect of free ATP4−, the concentration of which, in the experimental conditions employed, is significant and varies according to the total concentration of the ATP–magnesium chloride (or ATP–manganese chloride) mixture. Free ATP4− behaves as a negative modifier of yeast pyruvate carboxylase. 4. The effect of high concentrations of Mg2+ (or Mn2+) on the kinetics of yeast pyruvate carboxylase can be explained as a deinhibition with respect to ATP4−, instead of a direct enzyme activation. 5. At pH6·5 manganese chloride is more effective than magnesium chloride as enzyme activator even in the presence of a great excess (16-fold) of the latter. This is consistent with a significant contribution of the MnATP2− complex to the activity of yeast pyruvate carboxylase, in medium conditions resembling those existing inside the yeast cell (pH6·25–6·75; 12mm-magnesium chloride and 0·75mm-manganese chloride). 6. The physiological significance of the enzyme inhibition by free ATP4− is doubtful since the Mg2+ and Mn2+ concentrations reported to exist inside the yeast cell are sufficient to decrease ATP4− concentrations to ineffective values.

scholarly journals ISOLATION OF HEXOKINASE FROM BAKER'S YEAST

1946 ◽  
Vol 29 (6) ◽  
pp. 379-391 ◽  
Author(s):  
Louis Berger ◽  
Milton W. Slein ◽  
Sidney P. Colowick ◽  
Carl F. Cori
Keyword(s):  
Specific Activity ◽  
Proteolytic Enzymes ◽  
Protective Action ◽  
Fold Increase ◽  
Inhibitory Effect ◽  
Baker’S Yeast ◽  
Baker's Yeast ◽  
Thiol Compounds ◽  
Protective Proteins ◽  
Yeast Hexokinase

1. A method is described for the isolation of hexokinase from baker's yeast. The method is based mainly on fractionation with alcohol and results See PDF for Structure in a 30-fold increase in specific activity. The final product could be crystallized from ammonium sulfate without change in specific activity. 2. The enzyme catalyzes a transfer of phosphate from adenosinetriphosphate to glucose, fructose, or mannose, the relative rates with these three sugars being 1:1.4:0.3. 3. With glucose as substrate, the turnover number for the crystalline enzyme is 13,000 moles of substrate per 105 gm. of protein per minute at 30° and pH 7.5. The temperature coefficient (Q10°) between 0 and 30° is 1.9. 4. Magnesium ions are necessary for the activity, the dissociation constant for the Mg++ -protein complex being 2.6 x 10–3. Fluoride in concentrations as high as 0.125 M has no inhibitory effect on the enzyme when the Mg++ and orthophosphate concentrations are 6.5 x 10–3 M and 1 x 10–3 M, respectively. 5. The crystalline enzyme shows a loss in activity when highly diluted. This loss in activity can be prevented by diluting in the presence of small amounts of other proteins. Of the various protective proteins tested, insulin was the most effective, providing complete protection in a concentration of 6 micrograms per cc.; with serum albumin, a concentration of 60 micrograms per cc. was necessary. Thiol compounds (cysteine, glutathione) exerted no protective action. 6. The inactivation of the crystalline enzyme on incubation with trypsin can be prevented to a marked degree by the presence of glucose. The instability of crude preparations of yeast hexokinase may be attributed to the presence of proteolytic enzymes, since glucose or fructose has a remarkable protective effect on such preparations.

Inhibition of CO2 fixation in group D streptococci

1969 ◽  
Vol 15 (1) ◽  
pp. 57-60 ◽  
Author(s):  
Victor F. Lachica ◽  
Paul A. Hartman
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Pyruvate Carboxylase ◽  
Co2 Fixation ◽  
Tricarboxylic Acid Cycle ◽  
Inhibitory Effect ◽  
Tricarboxylic Acid ◽  
Acetyl Coa ◽  
Acid Cycle ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Group D

The stimulatory effect of acetyl-CoA and the inhibitory effect by L-aspartate and some intermediates of the tricarboxylic acid cycle in the assimilation of CO2 by crude extracts of group D streptococci suggest that the pyruvate carboxylase of Streptococcus faecium and the phosphoenolpyruvate carboxylase of S. bovis are allosteric enzymes. This implies that these enzymes are sites for the control of the amount of aspartate and of the tricarboxylic acid cycle intermediates synthesized.

scholarly journals The purification and some properties of 3-hydroxy-3-methylglutaryl-coenzyme A synthase from baker's yeast

1972 ◽  
Vol 126 (1) ◽  
pp. 27-34 ◽  
Author(s):  
B. Middleton ◽  
P. K. Tubbs
Keyword(s):  
Time Course ◽  
Specific Activity ◽  
Reaction Pathway ◽  
Gel Filtration ◽  
Baker’S Yeast ◽  
Baker's Yeast ◽  
Complete Protection ◽  
Acetyl Coa ◽  
Molecular Weights ◽  
Enzyme Intermediate

1. A purification of 3-hydroxy-3-methylglutaryl-CoA synthase from baker's yeast is described. This yields a preparation of average specific activity 2.1 units (μmol/min)/mg in which contamination by acetoacetyl-CoA thiolase is less than 0.2%. 2. The molecular weights of 3-hydroxy-3-methylglutaryl-CoA synthase and acetoacetyl-CoA thiolase from baker's yeast were determined by gel filtration on Sephadex G-200. The values obtained were 130000 and 190000 respectively. 3. 3-Hydroxy-3-methylglutaryl-CoA synthase is susceptible to irreversible inhibition by a wide variety of alkylating and acylating agents. The time-course of inhibition of the enzyme by some of these, including the active-site-directed inhibitor bromoacetyl-CoA, was studied in the presence and absence of substrates, products and product analogues. Acetyl-CoA, even when present at concentrations as low as 5μm, gives almost complete protection. Other acyl-CoA derivatives give some protection, but only at concentrations 10–30-fold higher. 4. These results are discussed with reference to an ordered reaction pathway in which acetyl-CoA reacts to give a covalent acetyl-enzyme intermediate.

Acetyl-CoA hydrolase: relation between activity and cholesterol metabolism in rat

1988 ◽  
Vol 255 (5) ◽  
pp. R724-R730
Author(s):  
S. Ebisuno ◽  
F. Isohashi ◽  
Y. Nakanishi ◽  
Y. Sakamoto
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Cholesterol Metabolism ◽  
Cholesterol Biosynthesis ◽  
Physiological Role ◽  
Competitive Inhibitor ◽  
Isobutyric Acid ◽  
Enzyme Linked Immunosorbent Assay ◽  
Acetyl Coa ◽  
Coa Hydrolase

To examine whether cytosolic acetyl-CoA hydrolase in rat liver is involved in regulation of cholesterol biosynthesis, we investigated the alteration of the enzyme activity under conditions of stimulation (cholestyramine treatment) and suppression [cholesterol feeding, a potent competitive inhibitor of microsomal 3-hydroxy-3-methylglutaryl-CoA reductase (CS 514) treatment, and a hypolipidemic drug [alpha-(p-chlorophenoxy)isobutyric acid, CPIB] injection) of cholesterol biosynthesis. The enzyme activity in rat liver increased significantly in the early diabetic, cholesterol-fed, CS 514-, and CPIB-treated groups, but no change in its activity was observed in chronic diabetic groups. Cholestyramine treatment to cholesterol-fed rats made the enzyme activity return to the initial level. When chronic diabetic rats were given a cholesterol diet or treated with CS 514 or CPIB, the activity increased significantly. Inhibition of cholesterol biosynthesis caused by these treatments induced increase in the enzyme activity with increase in the enzyme protein, judging from results obtained by enzyme-linked immunosorbent assay. These results suggest that this enzyme has a physiological role in maintenance of the equilibrium between the cytosolic acetyl-CoA concentration and CoA-SH pool for cholesterol metabolism.

Condensation of ?-ketobutyrate and acetyl-CoA in baker's yeast

1965 ◽  
Vol 50 (2) ◽  
pp. 164-170 ◽  
Author(s):  
J. L. Canovas ◽  
M. Ruiz-Amil ◽  
M. Losada
Keyword(s):  
Baker’S Yeast ◽  
Baker's Yeast ◽  
Acetyl Coa
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