Isopentenylgruppe

Isopentenylgruppe, in English often called the isopentenyl group or prenyl group, is a five-carbon substituent derived from isopentenyl pyrophosphate (IPP). It is a branched alkene fragment that attaches to substrates through the terminal carbon in many chemical and biological contexts.

Nomenclature and structure: The isopentenyl group is one of the basic five-carbon isoprenoid units. There are two common isomeric forms used in biology and chemistry: the isopentenyl group (3-methylbut-2-en-1-yl) and the dimethylallyl group (3,3-dimethylbut-2-en-1-yl). Both correspond to different branching patterns around the remaining three carbons of a butene skeleton, with a double bond in the chain.

Biosynthesis and precursors: In cells, the isopentenyl group originates from IPP, a central five-carbon building block produced by the mevalonate pathway or the non-mevalonate pathway. IPP and its isomer DMAPP serve as universal precursors for the construction of larger isoprenoids, such as farnesyl and geranylgeranyl units, used in diverse biosynthetic processes.

Biological roles: A well-known biological use is the transfer of an isopentenyl group to RNA molecules, notably in the modification of certain tRNAs where tRNA isopentenyltransferase attaches the group to adenosine at position 37, forming N6-isopentenyladenosine. In chemistry and pharmacology, isoprenylation (prenylation) of substrates is employed to modify lipophilicity and biological interactions, though larger prenyl donors are often involved in protein prenylation.

Nomenclature caveat: In older literature, the term prenyl is frequently used interchangeably with isopentenyl, but care is needed because cellular prenylation often uses longer donors such as farnesyl or geranylgeranyl groups.