Pyruvate kinase from the liver and kidney of Arapaima gigas

1978 ◽  
Vol 56 (4) ◽  
pp. 852-859 ◽  
Author(s):  
H. Guderley ◽  
J. H. A. Fields ◽  
J. M. Cardenas ◽  
P. W. Hochachka
Keyword(s):  
Pyruvate Kinase ◽  
Arapaima Gigas ◽  
Liver And Kidney ◽  
Low Levels ◽  
Pyruvate Kinases ◽  
Regulatory Properties ◽  
Partial Reversal

Pyruvate kinases from the kidney and liver of the osteoglossid Arapaima gigas were partially purified and characterized kinetically. The two enzymes have different elect rophoretic mobilities at pH 7.0, and while they share some qualitative similarities they show quantitative differences in their catalytic and regulatory properties. Both enzymes are activated by fructose 1.6-bisphosphate and inhibited by low levels of alanine and MgATP. The liver isozyme shows hyperbolic phosphoenolpyruvate binding, with a K1 for alanine inhibition of 0.7 mM and a K1 for MgATP inhibition of 1.0 mM. In contrast, the kidney isozyme shows cooperative phosphoenolpyruvate binding, which is accentuated at low levels of ADP. MgATP inhibition does not increase the cooperativity and shows an apparent K1 of 1.68 mM. The inhibition of alanine leads to considerable increases in the cooperativity and is effective at 1 mM and lower levels. Fructose 1.6-bisphosphate completely reverses the inhibition by alanine for both isozymes, while only leading to a partial reversal of the MgATP inhibition. These regulatory properties of both the kidney and the liver isozymes suit them for function in tissues which undergo both glycolysis and gluconeogenesis.

Catalytic and regulatory properties of pyruvate kinase isozymes from octopus mantle muscle and liver

1976 ◽  
Vol 54 (6) ◽  
pp. 863-870 ◽  
Author(s):  
H. E. Guderley ◽  
K. B. Storey ◽  
J. H. A. Fields ◽  
P. W. Hochachka
Keyword(s):  
Pyruvate Kinase ◽  
Concerted Action ◽  
Mammalian Muscle ◽  
Rate Characteristic ◽  
Burst Swimming ◽  
Glycolytic Control ◽  
Slow Moving ◽  
Pyruvate Kinases ◽  
Regulatory Properties ◽  
Glycolytic Rate

The octopus is a relatively slow-moving animal that relies upon burst swimming to power its predatory activities. Pyruvate kinase (EC, 2.7.1.40), as one of the major glycolytic control sites, must be regulated in such a fashion to allow the increased glycolytic rate characteristic of burst metabolism. The mantle enzyme is regulated by the concerted action of ATP, arginine phosphate, and citrate. The Km for ADP was 0.28 mM and that for phosphoenolpyruvate (PEP), 0.25 mM. In contrast to many other invertebrate muscle pyruvate kinases, the enzyme is insensitive to fructose-1,6-diphosphate (FDP) activation.The pyruvate kinase from the liver is kinetically and electrophoretically distinct from the mantle enzyme. The liver isozyme has a considerably lower affinity for PEP (Km = 0.85 mM), is inhibited by ATP, citrate, and arginine phosphate, and is subject to a strong activation by FDP (Ka = 1 × 10−6). These differences between the pyruvate kinases from catabolic and synthetic tissues are reminiscent of the distinctions between mammalian muscle and liver pyruvate kinases.

scholarly journals Kinetic and regulatory properties of cytosolic pyruvate kinase from germinating castor oil seeds

1991 ◽  
Vol 279 (2) ◽  
pp. 495-501 ◽  
Author(s):  
F E Podestá ◽  
W C Plaxton
Keyword(s):  
Pyruvate Kinase ◽  
Castor Oil ◽  
Mixed Type ◽  
Competitive Inhibition ◽  
Ricinus Communis ◽  
Cytosolic Ph ◽  
Oil Seeds ◽  
Saturation Kinetics ◽  
Regulatory Properties

The kinetic and regulatory properties of cytosolic pyruvate kinase (PKc) isolated from endosperm of germinating castor oil seeds (Ricinus communis L.) have been studied. Optimal efficiency in substrate utilization (in terms of Vmax/Km for phosphoenolpyruvate or ADP) occurred between pH 6.7 and 7.4. Enzyme activity was absolutely dependent on the presence of a bivalent and a univalent metal cation, with Mg2+ and K+ fulfilling this requirement. Mg2+ binding showed positive and negative co-operativity at pH 6.5 (h = 1.6) and pH 7.2 (h = 0.69) respectively. Hyperbolic saturation kinetics were observed with phosphoenolpyruvate (PEP) and K+, whereas ADP acted as a mixed-type inhibitor over 1 mM. Glycerol (10%, v/v) increased the S0.5(ADP) 2.3-fold and altered the pattern of nucleotide binding from hyperbolic (h = 1.0) to sigmoidal (h = 1.79) without modifying PEP saturation kinetics. No activators were identified. ATP, AMP, isocitrate, 2-oxoglutarate, malate, 2-phosphoglycerate, 2,3-bisphosphoglycerate, 3-phosphoglycerate, glycerol 3-phosphate and phosphoglycolate were the most effective inhibitors. These metabolites yielded additive inhibition when tested in pairs. ATP and 3-phosphoglycerate were mixed-type inhibitors with respect to PEP, whereas competitive inhibition was observed for other inhibitors. Inhibition by malate, 2-oxoglutarate, phosphorylated triose sugars or phosphoglycolate was far more pronounced at pH 7.2 than at pH 6.5. Although 32P-labelling studies revealed that extensive phosphorylation in vivo of soluble endosperm proteins occurred between days 3 and 5 of seed germination, no alteration in the 32P-labelling pattern of 5-day-germinated endosperm was observed after 30 min of anaerobiosis. Moreover, no evidence was obtained that PKc was a phosphoprotein in aerobic or anoxic endosperms. It is proposed that endosperm PKc activity of germinating castor seeds is enhanced after anaerobiosis through concerted decreases in ATP levels, cytosolic pH and concentrations of several key inhibitors.

scholarly journals Pyruvate kinases have an intrinsic and conserved decarboxylase activity

2014 ◽  
Vol 458 (2) ◽  
pp. 301-311 ◽  
Author(s):  
Wenhe Zhong ◽  
Hugh P. Morgan ◽  
Matthew W. Nowicki ◽  
Iain W. McNae ◽  
Meng Yuan ◽  
...  
Keyword(s):  
Pyruvate Kinase ◽  
Dicarboxylic Acids ◽  
Enzyme Mechanism ◽  
Decarboxylase Activity ◽  
Solution Studies ◽  
Pyruvate Kinases

We provide an enzyme mechanism for the decarboxylase activity of pyruvate kinase which is conserved from protozoa to mammals. Structural and solution studies of range of related dicarboxylic acids suggest the decarboxylase activity is restricted to oxaloacetate as a substrate.

scholarly journals Characterization of cDNAs encoding isoforms of hamster 3 beta-hydroxysteroid dehydrogenase/delta 5-->4 isomerase

1998 ◽  
Vol 20 (1) ◽  
pp. 99-110 ◽  
Author(s):  
FM Rogerson ◽  
J Courtemanche ◽  
A Fleury ◽  
JG LeHoux ◽  
JI Mason ◽  
...  
Keyword(s):  
Hydroxysteroid Dehydrogenase ◽  
Cdna Libraries ◽  
Sexually Dimorphic ◽  
High Affinity ◽  
Liver And Kidney ◽  
Low Levels ◽  
Type 3

Western blot analyses of various hamster tissues reveal high levels of expression of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in adrenal and liver, and moderate levels of expression in kidney. The expression in liver is sexually dimorphic; very high levels of protein are observed in adult male liver but very low levels are seen in the female liver. Three distinct cDNAs encoding isoforms of 3 beta-HSD were isolated from hamster cDNA libraries. The type 1 isoform is a high-affinity dehydrogenase/isomerase expressed in adrenal and male kidney. The type 2 isoform is also a high-affinity dehydrogenase/isomerase expressed in kidney and male liver. The type 3 enzyme is a 3-ketosteroid reductase expressed predominantly in kidney. Sequencing of the clones showed that all three are structurally very similar, although types 1 and 2 share the greatest degree of similarity. Immunohistochemical staining for 3 beta-HSD in the adrenal was found throughout the adrenal cortex. In the kidney staining was confined to tubules, and in the liver, heavy staining was found in hepatocytes. The cloning of cDNAs for 3 beta-HSD from the liver and kidney should help in elucidating the function of this enzyme in these tissues.

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