Table II.

Kinetic analyses of RF2A and RF2B

SubstrateSubstrate StructureKm2-aKcatHill CoefficientKcat/Km
RF2ARF2BRF2ARF2BRF2ARF2ARF2B
μm s−1
Saturated aliphatic aldehydes
 Formaldehyde Embedded Image 110 ± 20540 ± 904.3 ± 0.315 ± 1NC2-b 0.390.03
 Acetaldehyde Embedded Image 2.4 ± 0.76.6 ± 0.8100 ± 3100 ± 272.8 ± 0.64323
 Propionaldehyde Embedded Image 3.5 ± 0.55.4 ± 0.772 ± 13130 ± 153.1 ± 0.72125
 Butyraldehyde Embedded Image 3.1 ± 0.62.6 ± 0.546 ± 3120 ± 213.1 ± 0.31843
 Valeraldehyde Embedded Image 1.5 ± 0.3Trace2-c 9.5 ± 22-d 3.2 ± 0.76.2
 Hexanal Embedded Image 2.0 ± 0.211 ± 23.7 ± 0.25.6
 Heptaldehyde Embedded Image 4.6 ± 1.030 ± 22.1 ± 0.96.5
 Octanal Embedded Image 7.3 ± 1.023 ± 33.9 ± 0.13.0
 Nonanal Embedded Image 9.5 ± 2.019 ± 33.0 ± 1.52.0
 Decylaldehyde Embedded Image 15 ± 0.414 ± 13.9 ± 0.20.92
Aromatic aldehydes
 Benzaldehyde Embedded Image 3.4 ± 0.930 ± 31.8 ± 0.88.8
 4-Nitrobenzaldehyde Embedded Image 7.4 ± 2.010 ± 23.1 ± 0.314
p-Anisaldehyde Embedded Image 0.9 ± 0.11.8 ± 0.1NC6.5
m-Anisaldehyde Embedded Image 2.1 ± 0.035.9 ± 1NC14
Trans-cinnamaldehyde Embedded Image 3.5 ± 0.331 ± 3NC8.8
o-Nitrocinnamaldehyde Embedded Image 3.0 ± 1.059 ± 6NC19
Unsaturated aliphatic
Aldehydes
 Acrolein (propenal) Embedded Image 13 ± 136 ± 3NC2.7
trans-2-hexenal Embedded Image 55 ± 75.2 ± 1NC0.10
trans-2-nonenal Embedded Image NC
 4-Hydroxy-2-nonenal (4-HNE) Embedded Image 1.1 ± 0.34.3 ± 1NC3.9
 Citral Embedded Image 3.0 ± 0.94.6 ± 0.6NC1.5
Retinal aldehydes
 9-cis-retinal Embedded Image
 All-trans-retinal Embedded Image
μm s−1
Other aldehydes
 Chloroacetaldehyde Embedded Image 11 ± 172 ± 3NC6.5
 Glycolaldehyde Embedded Image 9.6 ± 2500 ± 130100 ± 12153 ± 26NC110.29
 Pyruvic aldehyde Embedded Image 4.9 ± 16.2 ± 0.3NC1.2
 Indole-3-acetaldehyde Embedded Image 5.0 ± 18.2 ± 3NC1.7
 Indole-3-carboxyaldehyde Embedded Image
 2-Naphthaldehyde Embedded Image

ALDH activities of purified recombinant RF2A and RF2B proteins were assayed with a series of substrate concentrations for each aldehyde to determine the K m andK cat. Data represent averages from at least three experiments.

    • F2-aK m should be “apparent K m” for those substrates that show positive cooperativity.

    • F2-b  NC, No cooperativity was observed with aldehyde substrate.

    • F2-c  Trace, Only trace activity detected with 10 μg of purified enzyme.

    • F2-d  ALDH activity not detected with various aldehyde concentrations and in the presence of at least 10 μg of purified enzyme.