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Table 4 Kinetic parameters for PvANR1 in assays containing varying amounts of cyanidin and NADPH

From: Proanthocyanidin accumulation and transcriptional responses in the seed coat of cranberry beans (Phaseolus vulgaris L.) with different susceptibility to postharvest darkening

Varying substrate Product K 0.5
(μM)
K i
(μM)
V max
(nmol min−1 mg−1)
k cat
(s−1)
k cat /K 0.5
(s−1 M−1)
Cyanidin Epicatechina 114.2 ± 19.0 631.5 ± 119.9 11.57 ± 1.13 0.0072 ± 0.0007 65.4 ± 13.8
Cyanidin Catechina 116.5 ± 10.7 583.8 ± 116.1 8.32 ± 0.73 0.0052 ± 0.0004 45.4 ± 6.42
NADPH Epicatechinb 103.5 ± 7.4 - 3.34 ± 0.21 0.0021 ± 0.0001 20.1 ± 0.49
NADPH Catechinb 102.3 ± 7.8 - 2.44 ± 0.18 0.0015 ± 0.0001 14.9 ± 1.03
  1. The K cat (also referred to as turnover rate) was calculated using a molecular mass of 37.4 kDa for the final recombinant PvANR1 preparation, following removal of the His6 tag
  2. aA non-linear regression model for substrate inhibition (as described under Methods) was used to determine apparent kinetic parameters for cyanidin. These assays were performed at a fixed NADPH concentration of 800 μM
  3. bThe Hill equation was utilized to determine kinetic parameters for NADPH. These assays were performed at a fixed cyanidin concentration of 100 μM; the Hill coefficient for epicatechin and catechin formation was 2.5 ± 0.19 and 2.5 ± 0.15, respectively