Conditions for the assay of glutamate semialdehyde aminotransferase that overcome the problem of substrate instability.
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.
Pugh
C E
CE
Department of Biochemistry, University of Wales, Cardiff, United Kingdom.
Nair
S P
SP
Harwood
J L
JL
John
R A
RA
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
D005971:Glutamates; C057794:glutamate-1-semialdehyde; D007535:Isomerases; D019751:Intramolecular Transferases; C061049:glutamate-1-semialdehyde 2,1-aminomutase