TABLE 5.
Substrate specificity of the ARO10-dependent 2-oxo-acid-decarboxylase activity in S. cerevisiaea
Substrate | Enzyme activity nmol min−1 (mg protein)−1
|
|||
---|---|---|---|---|
IMZ0001 [(NH4)2SO4c] | IMZ002 [(NH4)2SO4c] | IMZ002 [phenylalaninec] | Ratiob | |
Phenylpyruvate | BDd | 61.75 ± 1.71 (100) | 270 ± 6.98 (100) | 4.37 |
α-Ketoisovalerate | BD | 16.75 ± 2.21 (27) | 78.25 ± 4.1 (29) | 4.67 |
α-Ketoisocaproate | BD | 25 ± 0.82 (40) | 118 ± 7.53 (44) | 4.72 |
α-Ketomethylvalerate | BD | 21 ± 1.63 (34) | 97 ± 6.68 (36) | 4.62 |
3-Methylthio-α-ketobutyrate | BD | 18.5 ± 1.29 (30) | 87.7 ± 7.69 (32) | 4.74 |
Pyruvate | BD | BD | BD |
Strain IMZ001 is pdc1Δ pdc5Δ pdc6Δ aro10Δ thi3Δ carrying the empty expression vector p426GPD (2μ URA3 TDH3p). Strain IMZ002 is the same strain carrying the plasmid pUDe001 (2μ URA3 TDH3p-ARO10). Both strains were grown in aerobic, ethanol-limited chemostat cultures with ammonia as the nitrogen source. Enzyme activities were assayed in cell extracts. Data are the average±average deviation of the mean from assays of two independent chemostat cultures. The relative 2-oxo acid activities, expressed as a percentage of phenylpyruvate activity, are in parentheses.
Ratio of phenylalanine versus (NH4)2SO4.
N source.
BD, below detection limit.