Table 1 2.3 in 21 - Hydroxypregnane 21 - O-malonylation, a crucial step in cardenolide biosynthesis, can be achieved by substrate-promiscuous BAHD-type phenolic glucoside malonyltransferases from Arabidopsis thaliana and homolog proteins from Digitalis lanata

Table 1 Several 21-hydroxypregnanes as well as other compounds were docked into the homology model of At PMaT1, At PMaT2, Dl MaT1 and their binding scores calculated. The empirical binding free energy (kcal mol 1) of the substrates in the catalytic site is shown. For acronyms and structures, see Materials & Methods, and Fig.2. Empirical binding free energies where the distance between the catalytic histidine and the hydroxy group to be acylated were deemed too large are not listed ().
SubstrateEmpirical binding free energy [kcal mol 1]At PMaT1At PMaT2Dl MaT13- O -Digitoxosylketol9.5–10.13- O -Benzoylketol9.6n.d.9.43- O -Acetylketol8.8––Ketol8.5––5α- Pregnan-21-ol-3,20-dione7.6n.d.–5β- Pregnan-21-ol-3,20-dione7.1n.d.8.75β- Pregnane-3β,21-diol-20-one6.9n.d.8.54-Pregnen-21-ol-3,20-dione6.8n.d.7.6Kaempferol 3- O -glucoside7.3–7.8Quercetin 3- O -glucoside7.3–7.3Phenyl glucoside an.d.6.2n.d.
a Used as a positive control for At PMaT2.