2-keto-3-L-arabinonate dehydratase (L-KdpD) and 2-keto-3-D-xylonate dehydratase (D-KdpD) are the third enzymes in the Weimberg pathway catalyzing the dehydration of respective 2-keto-3-deoxy sugar acids (KDP) to α-ketoglutaric semialdehyde (KGSA). The Weimberg pathway has been explored recently with respect to the synthesis of chemicals from L-arabinose and D-xylose. However, only limited work has been done toward characterizing these two enzymes. In this work, several new L-KdpDs and D-KdpDs were cloned and heterologously expressed in
Escherichia coli
. Following kinetic characterizations and kinetic stability studies, the L-KdpD from
Cupriavidus necator
(
Cn
L-KdpD) and D-KdpD from
Pseudomonas putida
(
Pp
D-KdpD) appeared to be the most promising variants from each enzyme class. Magnesium had no effect on
Cn
L-KdpD, whereas increased activity and stability were observed for
Pp
D-KdpD in the presence of Mg
2+
. Furthermore,
Cn
L-KdpD was not inhibited in the presence of L-arabinose and L-arabinonate, whereas
Pp
D-KdpD was inhibited with D-xylonate (I
50
of 75 mM), but not with D-xylose. Both enzymes were shown to be highly active in the one-step conversions of L-KDP and D-KDP.
Cn
L-KdpD converted > 95% of 500 mM L-KDP to KGSA in the first 2 h while
Pp
D-KdpD converted > 90% of 500 mM D-KDP after 4 h. Both enzymes in combination were able to convert 83% of a racemic mixture of D,L-KDP (500 mM) after 4 h, with both enzymes being specific toward the respective stereoisomer.
Key points
• L-KdpDs and D-KdpDs are specific toward L- and D-KDP, respectively.
• Mg
2+
affected activity and stabilities of D-KdpDs, but not of L-KdpDs.
• CnL-KdpD and PpD-KdpD converted 0.5 M of each KDP isomer reaching 95 and 90% yield.
• Both enzymes in combination converted 0.5 M racemic D,L-KDP reaching 83% yield.
Electronic supplementary material
The online version of this article (10.1007/s00253-020-10742-5) contains supplementary material, which is available to authorized users.