Biomaterial Database

Monovalent cation induced reassociation of formyltetrahydrofolate synthetase monitored by Rayleigh light scattering and enzymic activity. 1982

M de Renobales, and W Welch

It has been previously established that formyltetrahydrofolate synthetase isolated from Clostridium cylindrosporum is reversibly dissociated and inactivated in the absence of certain monovalent cations. In the present paper, the reassociation of monomeric, inactive enzyme to form tetrameric, active enzyme was monitored by Rayleigh light scattering and enzymic activity. Light-scattering measurements confirmed that the active enzyme is composed of four subunits of equal weight. With the assumption that the results of analytical ultracentrifugation are correct--that monomers and tetramers are the only species ever present at appreciable levels--the amount of tetramer formed during reassociation was calculated from the light-scattering data. Evidence for the accumulation of catalytically active intermediates was obtained by comparing the rate of association of monomers (detected by light scattering) to the rate of return of enzymic activity. The accumulation of intermediates was most strikingly seen at low monovalent cation concentration at low ionic strength. Evidence is also presented that sedimentation favors reassociation of the enzyme. The reassociation data were fit to a second-order reversible rate equation. Interestingly, although the data were derived from the same experiments, the kinetic plot based on light-scattering measurements yielded a straight line function with an abrupt change in slope about 10 min after initiation of reassociation, while plots based on enzymic activity measurements gave a single slope.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008025	Ligases	A class of enzymes that catalyze the formation of a bond between two substrate molecules, coupled with the hydrolysis of a pyrophosphate bond in ATP or a similar energy donor. (Dorland, 28th ed) EC 6.	Ligase,Synthetases,Synthetase
D008027	Light	That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.	Light, Visible,Photoradiation,Radiation, Visible,Visible Radiation,Photoradiations,Radiations, Visible,Visible Light,Visible Radiations
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D002414	Cations, Monovalent	Positively charged atoms, radicals or group of atoms with a valence of plus 1, which travel to the cathode or negative pole during electrolysis.	Monovalent Cation,Cation, Monovalent,Monovalent Cations
D003013	Clostridium	A genus of motile or nonmotile gram-positive bacteria of the family Clostridiaceae. Many species have been identified with some being pathogenic. They occur in water, soil, and in the intestinal tract of humans and lower animals.
D005574	Formate-Tetrahydrofolate Ligase	A carbon-nitrogen ligase that catalyzes the formation of 10-formyltetrahydrofolate from formate and tetrahydrofolate in the presence of ATP. In higher eukaryotes the enzyme also contains METHYLENETETRAHYDROFOLATE DEHYDROGENASE (NADP+) and METHENYLTETRAHYDROFOLATE CYCLOHYDROLASE activity.	Tetrahydrofolate Formylase,Formyltetrahydrofolate Synthetase,Formate Tetrahydrofolate Ligase,Formylase, Tetrahydrofolate,Ligase, Formate-Tetrahydrofolate,Synthetase, Formyltetrahydrofolate
D012542	Scattering, Radiation	The diversion of RADIATION (thermal, electromagnetic, or nuclear) from its original path as a result of interactions or collisions with atoms, molecules, or larger particles in the atmosphere or other media. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Radiation Scattering,Radiation Scatterings,Scatterings, Radiation
D046911	Macromolecular Substances	Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.	Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular