Skip to main content

Table 1 Starch biosynthetic enzyme activity in soluble protein extracts from parsnip and sugar beet tap-roots

From: Starch biosynthetic genes and enzymes are expressed and active in the absence of starch accumulation in sugar beet tap-root

  PGM AGPase SS SBE
Root tissue and developmental stage (Units converting 1 μmole G1P to G6P, μg soluble protein-1, min-1) (nmol ADP-glucose, μg soluble protein-1, min-1) (nmol ADP-glucose converted to starch, μg soluble protein-1, min-1) (nmol G1P converted to branched starch, μg soluble protein-1, min-1)
Parsnip 48 DAP (light) 0.09 ± 0.02a 0.006 ± 0.002a 0.46 ± 0.20a 0.33 ± 0.01ab
Parsnip 48 DAP (dark) 0.12 ± 0.06a 0.007 ± 0.003a 0.55 ± 0.18a 0.38 ± 0.03ab
Parsnip 61 DAP (light) 0.12 ± 0.06a 0.006 ± 0.002a 0.68 ± 0.30a 0.52 ± 0.10a
Parsnip 61 DAP (dark) 0.11 ± 0.06a 0.007 ± 0.003a 0.71 ± 0.10a 0.47 ± 0.02a
Sugar beet 41 DAP (light) 0.09 ± 0.02a 0.007 ± 0.001a 0.43 ± 0.13a 0.20 ± 0.07b
Sugar beet 41 DAP (dark) 0.11 ± 0.03a 0.008 ± 0.001a 0.41 ± 0.06a 0.22 ± 0.04b
Sugar beet 54 DAP (light) 0.09 ± 0.02a 0.006 ± 0.001a 0.38 ± 0.06a 0.29 ± 0.17ab
Sugar beet 54 DAP (dark) 0.07 ± 0.004a 0.007 ± 0.001a 0.50 ± 0.16a 0.22 ± 0.08b
  1. Samples were taken from parsnip tap-roots harvested 48 and 61 days after planting (DAP) and sugar beet tap-roots harvested 41 and 54 DAP. Enzyme activity of phosphoglucomutase (PGM), ADP-glucose pyrophosphorylase (AGPase), starch synthase (SS) and starch branching enzyme (SBE) were measured on crude extracts. Data are means ± SD of values from extracts derived from different homogenates of 3 pooled roots (n = 3). Columns sharing the same letters were not significantly different according to Tukey’s test (P = 0.05).