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DOI: 10.1055/s-0035-1565602
The occurrence of progesterone 5β-reductase is not limited to the Angiosperms, a functional enzyme was characterized from Picea sitchensis
Early steps in cardenolide biosynthesis are catalyzed by 3β-hydroxysteroid dehydrogenase (3βHSD), ketosteroidisomerase (KSI) and progesterone 5β-reductase (P5βR, [1]). Inspecting public data bases, a homologous cDNA sequence was detected with respect to Picea sitchensis. Following its transfer into E. coli, a recombinant enzyme was overexpressed owing the reduction of progesterone to 5β-pregnane-3,20-dione in a stereo-specific manner [2]. The small substrate 2-cyclohexene-1-on was also found to be reduced. This enzymatic data provide first-time evidence concerning the occurrence of P5βR within the Coniferales.
It is presently unclear what a role the newly detected enzyme, belonging to the broadly documented SDR family [3], could play in planta since P. sitchensis does not produce cardenolides. However, P5βRs are also involved in the iridoid biosynthesis [4, 5]. This hypothesis has to be proven for P. sitchensis in future.
References:
[1] Herl V et al., 2006
[2] Bauer P et al., 2010
[3] Thorn A et al. 2008
[4] Geu-Flores et al. 2014
[5] Munkert J et al. 2015