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Literature summary extracted from

  • Huang, B.; Keeling, P.L.; Hennen-Bierwagen, T.A.; Myers, A.M.
    Comparative invitro analyses of recombinant maize starch synthases SSI, SSIIa, and SSIII reveal direct regulatory interactions and thermosensitivity (2016), Arch. Biochem. Biophys., 596, 63-72.
    View publication on PubMed

Activating Compound

EC Number Activating Compound Comment Organism Structure
2.4.1.21 Glucan stimulates the isoform SSIIa and SSIII reaction rates Zea mays

Cloned(Commentary)

EC Number Cloned (Comment) Organism
2.4.1.21 expressed in Escherichia coli Rosetta2 (DE3) pLysS cells Zea mays

KM Value [mM]

EC Number KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
2.4.1.21 0.33
-
 ADP-alpha-D-glucose free isoform SSIII, at pH 8.0 and 30°C Zea mays
2.4.1.21 0.39
-
 ADP-alpha-D-glucose free isoform SSI, at pH 8.0 and 30°C Zea mays
2.4.1.21 0.84
-
 ADP-alpha-D-glucose free isoform SSIIa, at pH 8.0 and 30°C Zea mays

Molecular Weight [Da]

EC Number Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
2.4.1.21 70000
-
 x * 70000, isoform SSI, calculated from amino acid sequence Zea mays
2.4.1.21 77000
-
 x * 77000, isoform SSIIa, calculated from amino acid sequence Zea mays
2.4.1.21 180000
-
 x * 180000, isoform SSIII, calculated from amino acid sequence Zea mays

Organism

EC Number Organism UniProt Comment Textmining
2.4.1.21 Zea mays
-
-
-

Purification (Commentary)

EC Number Purification (Comment) Organism
2.4.1.21 Ni-NTA agarose column chromatography, and gel filtration Zea mays

Specific Activity [micromol/min/mg]

EC Number Specific Activity Minimum [µmol/min/mg] Specific Activity Maximum [µmol/min/mg] Comment Organism
2.4.1.21 6.16
-
 free isoform SSI, at pH 8.0 and 30°C Zea mays
2.4.1.21 6.33
-
 free isoform SSIII, at pH 8.0 and 30°C Zea mays
2.4.1.21 9.75
-
 free isoform SSIIa, at pH 8.0 and 30°C Zea mays

Substrates and Products (Substrate)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
2.4.1.21 ADP-alpha-D-glucose + glycogen
-
 Zea mays ADP + ?
-
 ?

Subunits

EC Number Subunits Comment Organism
2.4.1.21 ? x * 180000, isoform SSIII, calculated from amino acid sequence Zea mays
2.4.1.21 ? x * 70000, isoform SSI, calculated from amino acid sequence Zea mays
2.4.1.21 ? x * 77000, isoform SSIIa, calculated from amino acid sequence Zea mays

Synonyms

EC Number Synonyms Comment Organism
2.4.1.21 SSI isoform Zea mays
2.4.1.21 SSIIa isoform Zea mays
2.4.1.21 SSIII isoform Zea mays
2.4.1.21 starch synthase
-
 Zea mays

Temperature Stability [°C]

EC Number Temperature Stability Minimum [°C] Temperature Stability Maximum [°C] Comment Organism
2.4.1.21 37 50 pre-incubation at up to 45°C has no effect on the activity of isoform SSI. Isoform SSIIa is stimulated by preincubation at 37-45°C, while isoform SSIII activity is reduced by ca. 50% after brief incubation at 45°C. Isoform SSIII is stable during preincubation at 37°C. At 50°C all enzymes completely lose activity within 40 min Zea mays