title: Complexes of muscle aldolase in equilibrium with fructose 1,6-bisphosphate.
abstract: Minimum values for the content of covalent intermediates in the equilibria of muscle aldolase with its cleavable substrates have been determined by acid denaturation/precipitation. Ribulose 1,5-bisphosphate, a nonsubstrate that binds well to aldolase in the native state, does not form a covalent complex that is acid precipitable. The insoluble protein complexes with substrates fructose 1,6-bisphosphate and sedoheptulose 1,7-bisphosphate, representing approximately 50% and approximately 60% of total bound substrate, are much more stable in acid and alkali than that with substrate 5-deoxyfructose 1,6-bisphosphate, suggesting that they have the form of protein-bound N-glycosides. Whether such complexes exist on the enzyme in the native state in addition to being formed subsequent to denaturation is unresolved. Both the acid-precipitable and nonprecipitable forms of fructose 1,6-bisphosphate are converted to triose phosphate products at the same rate, providing no kinetic evidence for a pool that is not on the main reaction path. Total fructose 1,6-bisphosphate liganded to enzyme returns to the free solution about 9 times for each net cleavage reaction. It is still not clear whether this is limited by the cleavage step or by release of glyceraldehyde phosphate.
mesh_terms: D000818:Animals; D004355:Drug Stability; D005634:Fructose-Bisphosphate Aldolase / Q000378:metabolism*; D005635:Fructosediphosphates / Q000378:metabolism*; D005986:Glyceraldehyde 3-Phosphate / Q000378:metabolism; D006027:Glycosides / Q000032:analysis; D006598:Hexosediphosphates / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D010761:Phosphorus Radioisotopes; D011485:Protein Binding; D011489:Protein Denaturation; D011817:Rabbits; D013379:Substrate Specificity
chemical_list: D005635:Fructosediphosphates; D006027:Glycosides; D006598:Hexosediphosphates; D010761:Phosphorus Radioisotopes; D005986:Glyceraldehyde 3-Phosphate; D005634:Fructose-Bisphosphate Aldolase; C029063:fructose-1,6-diphosphate