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Purification and 4-aminobutyrate-2-oxoglutarate aminotransferase (EC 2.6.1.19) from rabbit brain is described. The method was used as a routine to give between 5 and 10mg of pure enzyme from 750 g of rabbit brain. The enzyme is a dimer made up of subunits each with a mol. wt. of 58000. An absorption spectrum of the freshly prepared enzyme shows peaks at 415 and 330 nm. Treatment of the enzyme with the substrate 4-amino-butyrate or glutamate produces a decrease in the 415 nm and an increase in the 330 nm peak. This conversion, which is attributed to an aldimine into ketimine step in the reaction, is sufficiently slow when 4-aminobutyrate is the substrate to allow it to be followed by stopped-flow spectrophotometry. A first-order rate constant was determined for this step (12s-1) and compared with the turnover number for the enzyme derived by steady-state methods (9.5S-1). The first-order rate constant when glutamate was used as substrate was estimated to be approx. 30s-1.
R A John, and
L J Fowler
August 1994,
Biochimica et biophysica acta,
R A John, and
L J Fowler
October 1983,
The Journal of biological chemistry,
R A John, and
L J Fowler
December 1986,
European journal of biochemistry,
R A John, and
L J Fowler
May 1986,
European journal of biochemistry,
R A John, and
L J Fowler
April 1978,
European journal of biochemistry,
R A John, and
L J Fowler
January 1985,
European journal of biochemistry,
R A John, and
L J Fowler
May 2006,
Biochemical pharmacology,
R A John, and
L J Fowler
August 1983,
FEBS letters,
R A John, and
L J Fowler
April 1983,
Journal of biochemistry,
R A John, and
L J Fowler
February 1978,
Biochimica et biophysica acta,
