Abstract
Full-length cDNA clones for the alpha- and beta-subunits of pyrophosphate-fructose 6-phosphate 1-phosphotransferase have been isolated from a cDNA expression library derived from potato tuber poly(A)+ RNA. The nucleotide sequences indicate that the alpha- and beta-subunits are related with about 40% of amino acid residues being identical. A comparison of the deduced amino acid sequences of both subunits of this enzyme with that of the major ATP-dependent fructose 6-phosphate 1-phosphotransferase from Escherichia coli (Shirakihara, Y., and Evans, P. R. (1988) J. Mol. Biol. 204, 973-994) showed little homology between the proteins except for regions involved in the binding of fructose 6-phosphate/fructose, 1,6-bisphosphate and possibly between regions binding pyrophosphate and the beta- and gamma-phosphates of ADP/ATP. A comparison of the derived secondary structures of the two subunits of the PPi-dependent enzyme with the known secondary structure of the E. coli ATP-dependent enzyme indicated that the overall structure of these enzymes is similar. These data suggest that catalytic activity resides on the beta-subunit of the pyrophosphate-dependent enzyme.
Highlights
The nucleotide sequences indicate that the
Biol. 204, 973-994) showed little homology between the proteins except for regions involved in the binding of fructose
PPi-dependent enzyme with the known secondary structure of the E. coli ATP-dependent enzyme indicated that the overall structure of these enzymes is similar. These data suggest that catalytic activity resides on the &subunit of the pyrophosphate-dependent enzyme
Summary
A comparison of the deduced amino acid sequences of both subunits of this enzyme with that of the major ATP-dependent fructose 6-phosphate l-phosphotransferase from Escherichia coli A comparison of the derived secondary structures of the two subunits of the PPi-dependent enzyme with the known secondary structure of the E. coli ATP-dependent enzyme indicated that the overall structure of these enzymes is similar These data suggest that catalytic activity resides on the &subunit of the pyrophosphate-dependent enzyme. The PPi-phosphofructokinase has been purified to homogeneity from potato tubers [9] It has a native n/r, of 265,000 and is a heterotetramer of two LY- and two P-subunits with subunit M, values of 65,000 and 60,000, respectively, as determined by SDS-PAGE electrophoresis [9, 10].
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