Identification and functional analysis of a new type of Z,E‐mixed prenyl reductase from mycobacteria

Abstract

Isoprenoids with reduced Z,E-mixed prenyl groups are found in various organisms. To date, only polyprenol reductases (PR-Dol) involved in dolichol biosynthesis have been identified as enzymes capable of reducing Z,Emixed prenyl groups. Although C 35 -isoprenoids with reduced Z,E-mixed prenyl groups are found in mycobacteria, Z,E-mixed heptaprenyl reductase (HepR) remains unidentified. In the present study, the identification and functional analysis of HepR was performed. No PR-Dol homolog gene was detected in the genome of Mycolicibacterium vanbaalenii. However, a homolog of geranylgeranyl reductase (GGR), which reacts with an all-E prenyl group as a substrate, was encoded in the genome; thus, we analyzed it as a HepR candidate. In vitro enzymatic assay and in vivo gene suppression analysis identified the GGR homolog as HepR and revealed that HepR catalyzes the reduction of xand E-prenyl units in Z,E-mixed heptaprenyl diphosphates, and C 35 -isoprenoids are mainly biosynthesized using E,E,E-geranylgeranyl diphosphate as a precursor. Thus, it was demonstrated that the Z,E-mixed prenyl reductase family exists in the GGR homologs. To the best of our knowledge, this is the first identification of a new type of Z,E-mixed prenyl reductase with no sequence homology to PR-Dol. The substrate specificity of HepR significantly differed from that of GGR, suggesting that it is a new enzyme. HepR homologs are widely distributed in mycobacterial genomes, and lipid analysis suggests that many strains, including pathogenic species, produce HepR metabolites. The discovery of this new enzyme will promote further research on Z,E-mixed isoprenoids.

Unraveling the multiplicity of geranylgeranyl reductases in Archaea: potential roles in saturation of terpenoids

“…Other paralogs from A. fulgidus were also investigated in this study; however, their expression did not lead to any alteration in the quinone profile of E. coli (Hemmi et al 2005 ). Such GGR paralogs have also been found in mycobacteria, one of which was recently identified as heptaprenyl reductase (HepR) (Abe et al 2022 ). HepR was able to reduce ω- and E - prenyl units in Z,E-mixed heptaprenyl diphosphates from Mycolicibacterium vanbaalenii (Abe et al 2022 ).…”

“…Such GGR paralogs have also been found in mycobacteria, one of which was recently identified as heptaprenyl reductase (HepR) (Abe et al 2022 ). HepR was able to reduce ω- and E - prenyl units in Z,E-mixed heptaprenyl diphosphates from Mycolicibacterium vanbaalenii (Abe et al 2022 ). The majority of GGR paralogs from archaea remain uncharacterized, and their presence has been correlated with the saturation states of polyterpenes in archaeal membranes (Guan et al 2011 ).…”