Biomaterial Database

Specific modification of an effector binding site of phosphofructokinase by pyridoxal phasphate. 1976

G Colombo, and R G Kemp

Conditions are described for the covalent modification of rabbit skeletal muscle phosphofructokinase by pyridoxal phosphate plus sodium borohydride to produce an enzyme that appears by a number of criteria to be modified at the citrate binding site. Evidence that modification occurs at this site is as follows. (1) Protection against activity loss due to modification is provided by the combination of MgATP and citrate, whereas neither low concentrations of citrate nor MgATP alone is effective. This is consistent with the increased affinity for citrate that is observed in the presence of MgATP. (2) The extensive changes in activity and equilibrium binding result from the incorporation of only 1 mol of pyridoxal phosphate per mol of protomer. (3) Modification greatly increases sensitivity to MgATP inhibition, an effect consistent with the known synergism between MgATP and citrate. (4) The affinity of the enzyme for both MgATP and MgIPT at the catalytic site is increased by the modification. (5) The sensitivity of the enzyme to citrate inhibition is greatly diminished following covalent modification. (6) Modification abolishes the equilibrium binding of citrate. (7) Enhanced binding of MgATP is observed following modification, a result consistent with the enhancement of MgATP binding by citrate. Phosphofructokinase protected by citrate plus MgATP can also be modified by the incorporation of 1 or more mol of pyridoxal phosphate, but the enzyme so produced is capable of interacting with citrate and shows none of the properties herein described for the enzyme modified in the absence of citrate.

UI	MeSH Term	Description	Entries
D007292	Inosine Nucleotides		Inosine Phosphates,Nucleotides, Inosine,Phosphates, Inosine
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008024	Ligands	A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)	Ligand
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D010732	Phosphofructokinase-1	An allosteric enzyme that regulates glycolysis by catalyzing the transfer of a phosphate group from ATP to fructose-6-phosphate to yield fructose-1,6-bisphosphate. D-tagatose- 6-phosphate and sedoheptulose-7-phosphate also are acceptors. UTP, CTP, and ITP also are donors. In human phosphofructokinase-1, three types of subunits have been identified. They are PHOSPHOFRUCTOKINASE-1, MUSCLE TYPE; PHOSPHOFRUCTOKINASE-1, LIVER TYPE; and PHOSPHOFRUCTOKINASE-1, TYPE C; found in platelets, brain, and other tissues.	6-Phosphofructokinase,6-Phosphofructo-1-kinase,Fructose-6-P 1-Kinase,Fructose-6-phosphate 1-Phosphotransferase,6 Phosphofructokinase,Phosphofructokinase 1
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D011732	Pyridoxal Phosphate	This is the active form of VITAMIN B 6 serving as a coenzyme for synthesis of amino acids, neurotransmitters (serotonin, norepinephrine), sphingolipids, aminolevulinic acid. During transamination of amino acids, pyridoxal phosphate is transiently converted into pyridoxamine phosphate (PYRIDOXAMINE).	Pyridoxal 5-Phosphate,Pyridoxal-P,Phosphate, Pyridoxal,Pyridoxal 5 Phosphate,Pyridoxal P
D011817	Rabbits	A burrowing plant-eating mammal with hind limbs that are longer than its fore limbs. It belongs to the family Leporidae of the order Lagomorpha, and in contrast to hares, possesses 22 instead of 24 pairs of chromosomes.	Belgian Hare,New Zealand Rabbit,New Zealand Rabbits,New Zealand White Rabbit,Rabbit,Rabbit, Domestic,Chinchilla Rabbits,NZW Rabbits,New Zealand White Rabbits,Oryctolagus cuniculus,Chinchilla Rabbit,Domestic Rabbit,Domestic Rabbits,Hare, Belgian,NZW Rabbit,Rabbit, Chinchilla,Rabbit, NZW,Rabbit, New Zealand,Rabbits, Chinchilla,Rabbits, Domestic,Rabbits, NZW,Rabbits, New Zealand,Zealand Rabbit, New,Zealand Rabbits, New,cuniculus, Oryctolagus
D002951	Citrates	Derivatives of CITRIC ACID.