scholarly journals Conductance, Dissociation Constant and Thermodynamic Parameters Studies of Succinic acid in Water + Pyruvate Carboxylase and Water + Tetrahydrofuran medium

2021 ◽  
Vol 37 (6) ◽  
pp. 1440-1446
Author(s):  
Ashoke Hazra
Keyword(s):  
Succinic Acid ◽  
Dissociation Constant ◽  
Thermodynamic Parameters ◽  
Pyruvate Carboxylase ◽  
Limiting Molar Conductivities

Present paper describes the conductivity studies of succinic acid with aqueous PC and THF medium. Limiting molar conductivities and dissociation constant (Kc) were calculated by Kraus-Bray conductivity equations from 288K to 318K. Thermodynamic parameters ∆H, ∆G, ∆S, ∆Es were calculated.

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 Effects of Growth Mode and Pyruvate Carboxylase on Succinic Acid Production by Metabolically Engineered Strains of Escherichia coli

2002 ◽  
Vol 68 (4) ◽  
pp. 1715-1727 ◽  
Author(s):  
G. N. Vemuri ◽  
M. A. Eiteman ◽  
E. Altman
Keyword(s):  
Escherichia Coli ◽  
Succinic Acid ◽  
Pyruvate Carboxylase ◽  
Isocitrate Lyase ◽  
Tricarboxylic Acid Cycle ◽  
Metabolic Flexibility ◽  
Dual Phase ◽  
Anaerobic Conditions ◽  
Carboxylase Activity ◽  
Lyase Activity

ABSTRACT Escherichia coli NZN111, which lacks activities for pyruvate-formate lyase and lactate dehydrogenase, and AFP111, a derivative which contains an additional mutation in ptsG (a gene encoding an enzyme of the glucose phophotransferase system), accumulate significant levels of succinic acid (succinate) under anaerobic conditions. Plasmid pTrc99A-pyc, which expresses the Rhizobium etli pyruvate carboxylase enzyme, was introduced into both strains. We compared growth, substrate consumption, product formation, and activities of seven key enzymes (acetate kinase, fumarate reductase, glucokinase, isocitrate dehydrogenase, isocitrate lyase, phosphoenolpyruvate carboxylase, and pyruvate carboxylase) from glucose for NZN111, NZN111/pTrc99A-pyc, AFP111, and AFP111/pTrc99A-pyc under both exclusively anaerobic and dual-phase conditions (an aerobic growth phase followed by an anaerobic production phase). The highest succinate mass yield was attained with AFP111/pTrc99A-pyc under dual-phase conditions with low pyruvate carboxylase activity. Dual-phase conditions led to significant isocitrate lyase activity in both NZN111 and AFP111, while under exclusively anaerobic conditions, an absence of isocitrate lyase activity resulted in significant pyruvate accumulation. Enzyme assays indicated that under dual-phase conditions, carbon flows not only through the reductive arm of the tricarboxylic acid cycle for succinate generation but also through the glyoxylate shunt and thus provides the cells with metabolic flexibility in the formation of succinate. Significant glucokinase activity in AFP111 compared to NZN111 similarly permits increased metabolic flexibility of AFP111. The differences between the strains and the benefit of pyruvate carboxylase under both exclusively anaerobic and dual-phase conditions are discussed in light of the cellular constraint for a redox balance.

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