Table 1.

ADP-Glc–Dependent Starch Synthesis in Amyloplasts Isolated from T. aestivum Endosperm

Hexose Incorporation (nmol mg protein−1 h−1)
IncubationTotal StarchAmylose FractionAmylopectin FractionRecovery
ADP-Glc
    Intact1729 ± 247955 ± 66227 ± 5168%
    Broken679 ± 115382 ± 2791 ± 1670%
    Net1050 ± 87573 ± 35136 ± 27
ADP-Glc + ATP
    Intact3705 ± 3881480 ± 4131187 ±12072%
    Broken1551 ± 429669 ± 92551 ± 3478%
    Net2154 ± 318811 ± 194636 ± 48
  • Intact amyloplasts were incubated with 5 mM ADP-[U-14C]-Glc with or without 1 mM ATP for 30 min at 25°C. Amyloplasts used were 58 to 67% intact, judged by the latency of the marker enzyme alkaline inorganic pyrophosphatase. Material insoluble in methanol-KCl was fractionated using a thymol precipitation technique, and the amount of 14C recovered in each fraction was determined. Results presented are the mean and standard deviations of three independent experiments after subtracting 14C recovered in incubations stopped at zero time by the addition of 10% (w/v) trichloroacetic acid.