The plastidic phosphoglucomutase from Arabidopsis. A reversible enzyme reaction with an important role in metabolic control.
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.
Periappuram
C
C
Plant Biotechnology Institute, National Research Council of Canada, 110 Gymnasium Place, Saskatoon, SK S7N OW9, Canada.
Steinhauer
L
L
Barton
D L
DL
Taylor
D C
DC
Chatson
B
B
Zou
J
J
D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D018076:DNA, Complementary; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D010733:Phosphoglucomutase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010938:Plant Oils / Q000378:metabolism; D018087:Plastids / Q000201:enzymology*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D018076:DNA, Complementary; D010938:Plant Oils; D011994:Recombinant Proteins; D010733:Phosphoglucomutase