title: Conditions for the assay of glutamate semialdehyde aminotransferase that overcome the problem of substrate instability.
abstract: Investigations into the kinetic properties of glutamate semialdehyde aminotransferase, a key enzyme in the metabolic pathway leading to chlorophyll, are made difficult by the instability of the enzyme's substrate glutamate 1-semialdehyde. The rate of spontaneous disappearance of this compound from solution is shown to vary with the square of its concentration and to be pH-dependent. Thus using conditions appropriate to the assay of the enzyme, half of the substrate is lost from solution in a few minutes. Second-order rate constants for the reaction are determined and conditions are selected whereby the effects of the spontaneous reaction are rendered insignificant. The steady-state kinetic properties of the enzyme determined using these conditions are reported.
authors.affiliation: Department of Biochemistry, University of Wales, Cardiff, United Kingdom.
authors.forename: C E
authors.initials: CE
authors.lastname: Pugh
authors.forename: S P
authors.initials: SP
authors.lastname: Nair
authors.forename: J L
authors.initials: JL
authors.lastname: Harwood
authors.forename: R A
authors.initials: RA
authors.lastname: John
mesh_terms: D002736:Chloroplasts / Q000201:enzymology*; D005971:Glutamates / Q000378:metabolism*; D001467:Hordeum / Q000201:enzymology; D006863:Hydrogen-Ion Concentration; D019751:Intramolecular Transferases; D007535:Isomerases / Q000032:analysis* / Q000302:isolation & purification; D007700:Kinetics
chemical_list: D005971:Glutamates; C057794:glutamate-1-semialdehyde; D007535:Isomerases; D019751:Intramolecular Transferases; C061049:glutamate-1-semialdehyde 2,1-aminomutase