Cloning of the SNG1 gene of Arabidopsis reveals a role for a serine carboxypeptidase-like protein as an acyltransferase in secondary metabolism.
Serine carboxypeptidases contain a conserved catalytic triad of serine, histidine, and aspartic acid active-site residues. These enzymes cleave the peptide bond between the penultimate and C-terminal amino acid residues of their protein or peptide substrates. The Arabidopsis Genome Initiative has revealed that the Arabidopsis genome encodes numerous proteins with homology to serine carboxypeptidases. Although many of these proteins may be involved in protein turnover or processing, the role of virtually all of these serine carboxypeptidase-like (SCPL) proteins in plant metabolism is unknown. We previously identified an Arabidopsis mutant, sng1 (sinapoylglucose accumulator 1), that is defective in synthesis of sinapoylmalate, one of the major phenylpropanoid secondary metabolites accumulated by Arabidopsis and some other members of the Brassicaceae. We have cloned the gene that is defective in sng1 and have found that it encodes a SCPL protein. Expression of SNG1 in Escherichia coli demonstrates that it encodes sinapoylglucose:malate sinapoyltransferase, an enzyme that catalyzes a transesterification instead of functioning like a hydrolase, as do the other carboxypeptidases. This finding suggests that SCPL proteins have acquired novel functions in plant metabolism and provides an insight into the evolution of secondary metabolic pathways in plants.
Lehfeldt
C
C
Leibniz-Institut für Pflanzenbiochemie, Halle (Saale), Germany.
Shirley
A M
AM
Meyer
K
K
Ruegger
M O
MO
Cusumano
J C
JC
Viitanen
P V
PV
Strack
D
D
Chapple
C
C
D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D002268:Carboxypeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D003373:Coumaric Acids / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D004952:Esters / Q000378:metabolism; D005453:Fluorescence; D017353:Gene Deletion; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D010641:Phenotype; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D018749:RNA, Plant / Q000032:analysis / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D014466:Ultraviolet Rays
D003373:Coumaric Acids; D004952:Esters; D012333:RNA, Messenger; D018749:RNA, Plant; D011994:Recombinant Proteins; C073734:sinapinic acid; D000217:Acyltransferases; C416511:sinapoylglucose malate sinapoyltransferase; D002268:Carboxypeptidases; C022633:serine carboxypeptidase