Table 1.

GSS enzymatic reaction constants for aliphatic, aromatic, and indolic glucosinolates

GS (common name)GS (scientific name)GS typenKm, mMvmax, μmol⋅mg−1⋅min−1
Sinigrin2-Propenyl GSAliphatic31.61  ± 0.10168.7  ± 7.6
GlucotropaeolinBenzyl GSAromatic31.40  ± 0.13174.9  ± 7.6
Glucobrassicin3-Indoylmethyl GSIndolic22.33  ± 0.3066.6  ± 7.6
  • GSS amount was quantified photometrically. 0.2 μg natively purified protein were used in each assay. Reactions were carried out for 3 min in 75 mM Tris⋅HCl, pH 7.5, at 24°C, then 400 μl methanol were added to stop the reaction, and desulfo-glucosinolates were quantified by HPLC. Sinigrin and glucotropaeolin were tested in concentrations from 0.1 mM to 25 mM; for glucobrassicin the maximum concentration was 10 mM, because of limitations in the amount of purified substrate. GS, glucosinolate. Given are mean values ± SE; n indicates the number of experimental replicates.