Open AccessThe Plastidic Phosphoglucomutase from Arabidopsis. A Reversible Enzyme Reaction with an Important Role in Metabolic Control
Author(s) -
Cyril Periappuram,
Lee Steinhauer,
Dennis L. Barton,
David C. Taylor,
Brock Chatson,
Jitao Zou
Publication year - 2000
Publication title -
plant physiology (bethesda)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.554
H-Index - 312
eISSN - 1532-2548
pISSN - 0032-0889
DOI - 10.1104/pp.122.4.1193
Subject(s) - arabidopsis , biochemistry , mutant , biology , phosphoglucomutase , complementary dna , enzyme , arabidopsis thaliana , open reading frame , amino acid , gene , peptide sequence
An Arabidopsis cDNA (AtPGMp) encoding the plastidic phosphoglucomutase (PGM) predicted a 623-amino acid protein with an N-terminal sequence typical of a plastid signal peptide. Expression of a recombinant protein in Escherichia coli confirmed its enzyme activity. The recombinant enzyme had an apparent K(m) value of 98.5 microM and a V(max) of 4.48 micromol min(-1) (mg protein)(-1). The Calvin cycle intermediates fructose-1,6-bisphosphate and ribulose-1, 5-bisphosphate exerted an inhibitory effect on PGM activity, supporting its proposed involvement in controlling photosynthetic carbon flow. A point mutation was identified in the AtPGMp gene of the Arabidopsis pgm-1 mutant. The mutation in the mutant transcript generated a stop codon at about one third of the wild-type open reading frame, and thus rendered the polypeptide nonfunctional. Storage lipid analysis of the pgm-1 mutant seeds showed a 40% reduction in oil content compared with that of wild type. Our results indicate that plastidic PGM is an important factor affecting carbon flux in triacylglycerol accumulation in oilseed plants, most likely through its essential role in starch synthesis.