entkaurene

Ent-kaurene is a diterpene hydrocarbon with the molecular formula C20H34 and the ent-kaurane skeleton. It is a key intermediate in the biosynthesis of gibberellins, a class of plant hormones that regulate growth and development. The prefix “ent” denotes the stereochemical configuration relative to kaurene, reflecting its enantiomeric relationship to kaurene.

Biosynthesis and role in metabolism: In plants, the C20 isoprenoid geranylgeranyl pyrophosphate (GGPP) is first cyclized by ent-copalyl diphosphate synthase to ent-copalyl diphosphate. A second cyclization by ent-kaurene synthase yields ent-kaurene. This hydrocarbon is then oxidized by a sequence of cytochrome P450 enzymes, converting it to ent-kaurenoic acid and further to gibberellin intermediates such as GA12, GA53, and ultimately active gibberellins that regulate processes like seed germination, stem elongation, and flowering.

Occurrence and significance: Ent-kaurene is widespread in vascular plants, including gymnosperms and angiosperms, as part of the canonical gibberellin biosynthetic pathway. Although the final hormones are the gibberellins, ent-kaurene serves as the essential hydrocarbon precursor. Its presence and flux through the pathway are linked to developmental and growth responses in diverse plant species.

Structure and properties: As a hydrocarbon, ent-kaurene is nonpolar and lipophilic, typically extracted from plant tissues with organic solvents. It is a chiral molecule, representing the enantiomer of kaurene and belonging to the broader class of ent-kaurane diterpenes with a fused ring system.