Isolation of a highly active fructose diphosphatase from rabbit muscle: Its subunit structure and activation by monovalent cations (original) (raw)
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Kinetic properties of D-fructose-1,6-bisphosphate 1-phosphohydrolase isolated from human muscle
The Biochemical journal, 1995
D-Fructose-1,6-bisphosphate 1-phosphohydrolase (EC 3.1.3.11) [Fru(1,6)Pase] was isolated from human muscle in an electrophoretically homogeneous form, free of aldolase contamination. The enzyme is inhibited by the substrate [fructose (1,6)-bisphosphate]. Km is 0.77 microM; Kis is 90 microM. The fructose-2,6-bisphosphate [Fru(2,6)P2], a regulator of gluconeogenesis, inhibits human muscle Fru(1,6)Pase with Ki = 0.13 microM. To determine Km, Kis and Ki the integrated method was used. AMP is an allosteric inhibitor of Fru(1,6)Pase. As with other mammalian isoenzymes, the human muscle enzyme is more strongly inhibited by AMP than is the liver isoenzyme [Dzugaj and Kochman (1980) Biochim. Biophys. Acta 614, 407-412]. Both of the inhibitors [AMP and Fru(2,6)P2] act synergistically on human muscle Fru(1,6)Pase. Ki for Fru(2,6)P2 determined in the presence of 0.4 microM AMP was 0.028 microM. The human muscle enzyme, like other mammalian Fru(1,6)Pases, requires Mg2+ for its activity. The Ka f...
Journal of Biological Chemistry
Fructose-6-phosphate,2-kinase:fructose-2,6-bis-phosphatase from rat skeletal muscle has been purified to homogeneity, and its structure and kinetic properties have been determined. The Mr of the native enzyme was 100,000 and the subunit Mr was 54,000. The apparent Km values of fructose-6-P,2-kinase for Fru-6-P and ATP were 56 and 48 microM, respectively. The apparent Km value for Fru-2,6-P2 of fructose-2,6-bis-phosphatase was 0.4 microM, and the Ki for Fru-6-P was 12.5 microM. The enzyme was bifunctional, and the phosphatase activity was 2.5 times higher than the kinase activity. The enzyme was not phosphorylated by cAMP-dependent protein kinase. The amino acid composition of the skeletal muscle enzyme was similar to that of the rat liver enzyme, and the carboxyl terminus sequence (His-Tyr) was the same as that of the liver enzyme. The tryptic peptides generated from the liver and skeletal muscle enzymes were identical except for two peptides. A peptide corresponding to nucleotides ...
Univalent cation activation of fructose 1,6-diphosphatase
Archives of Biochemistry and Biophysics, 1970
Fructose 1,6-diphosphatase from several vertebrate sources has been studied with respect to univalent cation activation. All the enzymes tested showed activation by certain univalent cations, K+ or NH,+ being the best activators. A re-evaluation of some properties of fructose 1,6-diphosphatases in the presence of univalent cation activators showed, as studied with pig kidney, rabbit liver, and rabbit muscle fructose 1,6-diphosphatase, that the MgZ+-saturation curves were markedly altered by the presence of 150 mu K+. Not only an increase in K, and Tim,, was observed, but also the sigmoidal nature of the Mg?saturation curves became evident. AMP inhibition, characteristic of most fructose 1,6-diphosphatases, was not significantly altered by the presence of K+ in the case of pig kidney, rabbit liver, and fish (Roja chilensis) liver fructose 1,6-diphosphatase. Rabbit muscle fructose 1,6-diphosphatase became more sensitive to AMP inhibition, while in the case of fish (Genipterus chilensis) liver fructose 1,6-diphosphatase, inhibition by AMP could only be demonstrated in the presence of the univalent cation activators.
Biochemistry, 1966
Treatment of crystalline rabbit liver fructose diphosphatase (FDPase) with N-acetylimidazole results in a time-dependent 0-acetylation of ten tyrosyl residues. In the first phase of the reaction two to three tyrosyl residues are acetylated with no change in catalytic properties. The acetylation of four additional residues is associated with loss of allosteric inhibition by adenosGe monophosphate (AMP). Finally, with
Rabbit muscle fructose-1,6-bisphosphatase is phosphorylatedin vivo
Acta biochimica Polonica, 2003
Phosphorylated fructose-1,6-bisphosphatase (FBPase) was isolated from rabbit muscle in an SDS/PAGE homogeneous form. Its dephosphorylation with alkaline phosphatase revealed 2.8 moles of inorganic phosphate per mole of FBPase. The phosphorylated FBPase (P-FBPase) differs from the dephosphorylated enzyme in terms of its kinetic properties like K(m) and k(cat), which are two times higher for the phosphorylated FBPase, and in the affinity for aldolase, which is three times lower for the dephosphorylated enzyme. Dephosphorylated FBPase can be a substrate for protein kinase A and the amount of phosphate incorporated per FBPase monomer can reach 2-3 molecules. Since interaction of muscle aldolase with muscle FBPase results in desensitisation of the latter toward AMP inhibition (Rakus & Dzugaj, 2000, Biochem. Biophys. Res. Commun. 275, 611-616), phosphorylation may be considered as a way of muscle FBPase activity regulation.