Table I.

Distribution of enzyme activities within pea homogenates fractionated by discontinuous Suc gradient centrifugation (see Fig. 2)

Gradient FractionLatent UDPaseCyt c OxidaseNADH:Cytc ReductaseGalAT1-a
μmol PO4released min−1 μmol Cyt c oxidized min−1± se μmol Cyt c reduced min−1 ±se pmol GalA incorporated min−1 ±se
GV1-b 33.903.38 ± 0.121.46 ± 0.08
33%ND1-c 000
ER1-d 11.32.19 ± 0.156.21 ± 0.600
38%ND1-c 4.07 ± 0.203.98 ± 0.260
Pellet5.872.17 ± 0.472.74 ± 0.160.12 ± 0.08

Discontinuous Suc gradients were made and enzyme assays conducted as described in “Materials and Methods.” Total enzyme activity in each gradient fraction is shown. The data are the average of two replicates ± se from one gradient. Similar results were obtained in two independent gradients.

    • F1-a  Assayed using 1.1 μmUDP-[14C]GalA.

    • F1-b  The interface between the 8% and the 33% (w/w) Suc layers which is enriched in Golgi membranes.

    • F1-c  ND, Not determined due to the presence of phosphate in the buffer.

    • F1-d  The interface between the 33% and the 38% (w/w) Suc layers that is enriched in ER membranes.