Table 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 3 Comparison of the specific activities of r At PMaT1, r At PMaT2, r Dl MaT1 and r Dl MaT2 with different substrates. Concentration of substrate in the assay was 0.2 mM.
SubstrateEnzme activity (nkat mg 1)r At PMaT1r At PMaT2r Dl MaT1r Dl MaT23- O -Acetylketol6.80.33+0.015β- Pregnane-3β,21-diol-20-one0.290.140.030.025β- Pregnan-21-ol-3,20-dione0.510.180.050.024-Pregnen-21-ol-3,20-dione0.300.180.010.013- O -Digitoxosylketol2.20.190.010.02Kaempferol 3- O -glucoside111.0n.d.117.769.1Quercetin 3- O -glucoside125.0n.d.183.387.4Phenyl glucoside*n.d.34.8n.d.n.d.
n.d.: not determined;: specific activity <0.01 nkat mg 1
+ * used as a positive control for r At PMaT2.