TY - JOUR
T1 - Expression of Bovine Heart Fructose 6-Phosphate,2-kinase:Fructose 2,6-Bisphosphatase and Determination of the Role of the Carboxyl Terminus by Mutagenesis
AU - Abe, Y.
AU - Minami, Y.
AU - Li, Y.
AU - Nguyen, C.
AU - Uyeda, K.
PY - 1995/2
Y1 - 1995/2
N2 - Bovine heart fructose 6-P,2-kinase:fructose 2,6-bisphosphatase was expressed in Escherichia coli. In order to determine the role of the carboxyl-terminal peptide, 49 and 78 amino acids from the C-terminus were deleted using oligonucleotide-directed mutagenesis. The expressed wild-type and mutant enzymes were purified to homogeneity, and the steady-state kinetics of the mutant enzymes were compared to those of the wild-type enzyme. Deletion of 49 residues (Del 49) resulted in a 35% decrease in XmFra6P, a 36% increase in Vmax, and a 2-fold increase in kcat/Km of the kinase. There was no change in the kinetic properties of the phosphatase activity. Deletion of 78 residues (Del 78) resulted in a 4.5-fold decrease in KmFru6P, a 2.5-fold increase in Vmax, a 12-fold increase in kcat/Km of the kinase, and a 3-fold increase in kcat/Km of the phosphatase. Phosphorylation of the wild-type and Del 49 enzymes resulted in decreased XmFru6p and activation of the kinase without affecting the phosphatase activity. Thermal inactivation rates of the wild-type and Del 49 enzymes were similar, but the rate of Del 78 was more rapid. The phosphorylated wild-type and Del 49 enzymes were more sensitive to thermal inactivation than the dephospho forms. Urea inactivation of the kinase and phosphatase of wild-type and Del 49 were similar, but Del 78 was more sensitive to urea. All phosphorylated enzymes were more susceptible to urea inactivation. These results suggest that the C-terminal peptide of the enzyme, especially the region Phe453-Asn482, containing protein kinase A and C phosphorylation sites, is important in maintaining less active (T) states of the kinase and the phosphatase domains. Phosphorylation of the peptide converts the kinase to a more active (R) state without affecting the phosphatase, but deletion of the peptide results in activation of the phosphatase to R state.
AB - Bovine heart fructose 6-P,2-kinase:fructose 2,6-bisphosphatase was expressed in Escherichia coli. In order to determine the role of the carboxyl-terminal peptide, 49 and 78 amino acids from the C-terminus were deleted using oligonucleotide-directed mutagenesis. The expressed wild-type and mutant enzymes were purified to homogeneity, and the steady-state kinetics of the mutant enzymes were compared to those of the wild-type enzyme. Deletion of 49 residues (Del 49) resulted in a 35% decrease in XmFra6P, a 36% increase in Vmax, and a 2-fold increase in kcat/Km of the kinase. There was no change in the kinetic properties of the phosphatase activity. Deletion of 78 residues (Del 78) resulted in a 4.5-fold decrease in KmFru6P, a 2.5-fold increase in Vmax, a 12-fold increase in kcat/Km of the kinase, and a 3-fold increase in kcat/Km of the phosphatase. Phosphorylation of the wild-type and Del 49 enzymes resulted in decreased XmFru6p and activation of the kinase without affecting the phosphatase activity. Thermal inactivation rates of the wild-type and Del 49 enzymes were similar, but the rate of Del 78 was more rapid. The phosphorylated wild-type and Del 49 enzymes were more sensitive to thermal inactivation than the dephospho forms. Urea inactivation of the kinase and phosphatase of wild-type and Del 49 were similar, but Del 78 was more sensitive to urea. All phosphorylated enzymes were more susceptible to urea inactivation. These results suggest that the C-terminal peptide of the enzyme, especially the region Phe453-Asn482, containing protein kinase A and C phosphorylation sites, is important in maintaining less active (T) states of the kinase and the phosphatase domains. Phosphorylation of the peptide converts the kinase to a more active (R) state without affecting the phosphatase, but deletion of the peptide results in activation of the phosphatase to R state.
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U2 - 10.1021/bi00008a020
DO - 10.1021/bi00008a020
M3 - Article
C2 - 7873535
AN - SCOPUS:0028963164
SN - 0006-2960
VL - 34
SP - 2553
EP - 2559
JO - Biochemistry
JF - Biochemistry
IS - 8
ER -