Guyer_2018_J.Exp.Bot_69_879

Reference

Title : Catalytic and structural properties of pheophytinase, the phytol esterase involved in chlorophyll breakdown - Guyer_2018_J.Exp.Bot_69_879
Author(s) : Guyer L , Salinger K , Krugel U , Hortensteiner S
Ref : J Exp Bot , 69 :879 , 2018
Abstract :

During leaf senescence and fruit ripening, chlorophyll is degraded in a multistep pathway into linear tetrapyrroles called phyllobilins. A key feature of chlorophyll breakdown is the removal of the hydrophobic phytol chain that renders phyllobilins water soluble, an important prerequisite for their ultimate storage in the vacuole of senescent cells. Chlorophyllases had been considered for more than a century to catalyze dephytylation in vivo; however, this was recently refuted. Instead, pheophytinase was discovered as a genuine in vivo phytol hydrolase. While chlorophyllase acts rather unspecifically towards different porphyrin substrates, pheophytinase was shown to specifically dephytylate pheophytin, namely Mg-free chlorophyll. The aim of this work was to elucidate in detail the biochemical and structural properties of pheophytinase. By testing different porphyrin substrates with recombinant pheophytinase from Arabidopsis thaliana we show that pheophytinase has high specificity for the acid moiety of the ester bond, namely the porphyrin ring, while the nature of the alcohol, namely the phytol chain in pheophytin, is irrelevant. In silico modelling of the 3-dimensional structure of pheophytinase and subsequent analysis of site-directed pheophytinase mutant forms allowed the identification of the serine, histidine, and aspartic acid residues that compose the catalytic triad, a classical feature of serine-type hydrolases to which both pheophytinase and chlorophyllase belong. Based on substantial structural differences in the models of Arabidopsis pheophytinase and chlorophyllase 1, we discuss potential differences in the catalytic properties of these two phytol hydrolases.

PubMedSearch : Guyer_2018_J.Exp.Bot_69_879
PubMedID: 29036670
Gene_locus related to this paper: arath-Q9FFZ1

Related information

Gene_locus arath-Q9FFZ1
Family arath-Q9FFZ1    Pheophytinase

Citations formats

Guyer L, Salinger K, Krugel U, Hortensteiner S (2018)
Catalytic and structural properties of pheophytinase, the phytol esterase involved in chlorophyll breakdown
J Exp Bot 69 :879

Guyer L, Salinger K, Krugel U, Hortensteiner S (2018)
J Exp Bot 69 :879