Premium
Role of a GDSL lipase‐like protein as sinapine esterase in Brassicaceae
Author(s) -
Clauß Kathleen,
Baumert Alfred,
Nimtz Manfred,
Milkowski Carsten,
Strack Dieter
Publication year - 2008
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2007.03374.x
Subject(s) - lipase , biochemistry , catalytic triad , esterase , arabidopsis , brassicaceae , chemistry , myrosinase , enzyme , amino acid , biology , glucosinolate , brassica , serine , gene , botany , mutant
Summary The seeds of most members of the Brassicaceae accumulate high amounts of sinapine (sinapoylcholine) that is rapidly hydrolyzed during early stages of seed germination. One of three isoforms of sinapine esterase activity (BnSCE3) has been isolated from Brassica napus seedlings and subjected to trypsin digestion and spectrometric sequencing. The peptide sequences were used to isolate BnSCE3 cDNA, which was shown to contain an open reading frame of 1170 bp encoding a protein of 389 amino acids, including a leader peptide of 25 amino acids. Sequence comparison identified the protein as the recently cloned BnLIP2, i.e. a GDSL lipase‐like protein, which displays high sequence identity to a large number of corresponding plant proteins, including four related Arabidopsis lipases. The enzymes belong to the SGNH protein family, which use a catalytic triad of Ser‐Asp‐His, with serine as the nucleophile of the GDSL motif. The corresponding B. napus and Arabidopsis genes were heterologously expressed in Nicotiana benthamiana leaves and proved to confer sinapine esterase activity. In addition to sinapine esterase activity, the native B. napus protein (BnSCE3/BnLIP2) showed broad substrate specificity towards various other choline esters, including phosphatidylcholine. This exceptionally broad substrate specificity, which is common to a large number of other GDSL lipases in plants, hampers their functional analysis. However, the data presented here indicate a role for the GDSL lipase‐like BnSCE3/BnLIP2 as a sinapine esterase in members of the Brassicaceae, catalyzing hydrolysis of sinapine during seed germination, leading, via 1‐ O ‐sinapoyl‐β‐glucose, to sinapoyl‐ l ‐malate in the seedlings.