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Petroselinum crispum prenyl transferase (PcPT)

Structure of PcPT enzyme

Prenylates umbelliferone in the presence of dimethylallyl diphosphate (DMAPP) at the 6 position to yield demethylsuberosin (DMS) as the main product, together with a minor amount of osthenol corresponding to 8-prenylated umbelliferone.

--Prenylation== Prenylation is a structural modification in which an isoprenoid moiety, prenyl being the most common, is transferred from a donor molecule to an acceptor. Prenylation of aromatic substrates is known to enhance their bioactivity and is an essential step in the biosynthesis of biologically active secondary metabolites, which play an integral role in the survival and disease resistance of many plant species. To perform prenylation, plants use membrane-bound aromatic prenyltransferases (PTs) that transfer isoprenoid moieties from pyrophosphate donor substrates to aromatic acceptor substrates.

PcPT is a transmembrane proteins with 8 predicted transmembrane helices. The gene was first isolated by designing degenerate primers based on conserved amino acids in other already identified aromatic PTs. Using these primers, a PCR-based strategy was used to clone a PT cDNA from parsley (Petroselinum crispum) leaves, which was named PcPT. PcPT gene expression was found throughout the parsley plant, and was increased by UV irradiation. The subcellular localization of PcPT was demonstrated to be plastids.

Functional characterization of PcPT in a transient expression system with Nicotiana benthamiana showed that PcPT shows prenylation activity for umbelliferone with strong substrate specificity for dimethylallyl diphosphate (DMAPP) as a prenyl donor, dominant prenylation activity on umbelliferone at C6 leading to DMS, and minor activity at C8 of umbelliferone leading to osthenol. PcPT contains a cleavage site for a signal peptide sequence (48 aa) at the N-terminus. Using GFP-fusion based experiments, the results strongly suggest that PcPT functions in plastids, where it utilized DMAPP as a prenyl donor.

Sequence and Features