Functional homology of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase, phosphoglycerate mutase, and 2,3-bisphosphoglycerate mutase.
The bisphosphatase domain of the rat liver 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase has been shown to exhibit a structural similarity to yeast phosphoglycerate mutase and human red blood cell 2,3-bisphosphoglycerate mutase including very similar active site sequences with a histidyl residue being involved in phospho group transfer. The liver bifunctional enzyme was found to catalyze the hydrolysis of glycerate 1,3-bisphosphate to glycerate 3-phosphate and inorganic phosphate. The Km for glycerate 1,3-bisphosphate was 320 microM and the Vmax was 11.5 milliunits/mg. Incubation of the rat liver enzyme with [1-32P]glycerate 1,3-bisphosphate resulted in the formation of a phosphoenzyme intermediate, and the labeled amino acid was identified as 3-phosphohistidine. Tryptic and endoproteinase Lys-C peptide maps of the 32P-phosphoenzyme labeled either with [2-32P]fructose 2,6-bisphosphate or [1-32P]glycerate 1,3-bisphosphate revealed that 32P-radioactivity was found in the same peptide, proving that the same histidyl group accepts phosphate from both substrates. Fructose 2,6-bisphosphate inhibited competitively the formation of phosphoenzyme from [1-32P]glycerate 1,3-bisphosphate. Effectors of fructose-2,6-bisphosphatase also inhibited phosphoenzyme formation. Substrates and products of phosphoglycerate mutase and 2,3-bisphosphoglycerate mutase also modulated the activities of the bifunctional enzyme. These results demonstrate that, in addition to a structural homology, the bisphosphatase domain of the bifunctional enzyme has a functional similarity to phosphoglycerate mutase and 2,3-bisphosphoglycerate mutase and support the concept of an evolutionary relationship between the three enzyme activities.
Tauler
A
A
Department of Physiology and Biophysics, School of Medicine, State University of New York, Stony Brook 11794.
el-Maghrabi
M R
MR
Pilkis
S J
SJ
D000255:Adenosine Triphosphate / Q000378:metabolism; D001731:Bisphosphoglycerate Mutase / Q000378:metabolism*; D004163:Diphosphoglyceric Acids / Q000378:metabolism; D004912:Erythrocytes / Q000201:enzymology; D006358:Hot Temperature; D006801:Humans; D007535:Isomerases / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D010449:Peptide Mapping; D025481:Phosphofructokinase-2; D010736:Phosphoglycerate Mutase; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism*; D013329:Structure-Activity Relationship
D004163:Diphosphoglyceric Acids; D000255:Adenosine Triphosphate; D010770:Phosphotransferases; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases; D007535:Isomerases; D010736:Phosphoglycerate Mutase; D001731:Bisphosphoglycerate Mutase