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Literature summary for 2.4.1.21 extracted from

  • Gao, Z.; Keeling, P.; Shibles, R.; Guan, H.
    Involvement of lysine-193 of the conserved "K-T-G-G" motif in the catalysis of maize starch synthase IIa (2004), Arch. Biochem. Biophys., 427, 1-7.
    View publication on PubMed
Search for more literature for 2.4.1.21

Cloned(Commentary)

Cloned (Comment) Organism
-
 Zea mays

Protein Variants

Protein Variants Comment Organism
K193E mutation does not alter the binding of ADP-glucose, Km-value for amylopectin is 3.6fold higher than the wild-type value, KM-value for glycogen is 3.2fold lower than the wild-type value Zea mays
K193Q mutation does not alter the binding of ADP-glucose, Km-value for amylopectin is 1.5fold lower than the wild-type value, KM-value for glycogen is 15.5fold lower than the wild-type value Zea mays
K193R mutation does not alter the binding of ADP-glucose, Km-value for amylopectin is 2.6fold higher than the wild-type value, KM-value for glycogen is 2.5fold lower than the wild-type value Zea mays

Inhibitors

Inhibitors Comment Organism Structure
pyridoxal-5'-phosphate inactivates starch synthase IIa, ADP-glucose protects from inactivation Zea mays

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
 additional information Km-values for amylopectin: 0.2 mg/ml for wild-type enzyme, 0.53 mg/ml for mutant enzyme K193R, 0.13 mg/ml for mutant enzyme K193Q, 0.72 mg/ml for mutant enzyme K193E. Km-values for glycogen: 0.17 mg/ml for wild-type enzyme, 0.68 mg/ml for mutant enzyme K193R, 0.11 mg/ml for mutant enzyme K193Q, 0.53 mg/ml for mutant enzyme K193E Zea mays
0.1
-
 ADP-glucose mutant enzyme K193Q, glycogen as primer Zea mays
0.11
-
 ADP-glucose wild-type enzyme, amylopectin as primer Zea mays
0.13
-
 ADP-glucose wild-type enzyme, glycogen as primer Zea mays
0.14
-
 ADP-glucose mutant enzyme K193Q, amylopectin as primer Zea mays
0.15
-
 ADP-glucose mutant enzyme K193R, amylopectin as primer Zea mays
0.15
-
 ADP-glucose mutant enzyme K193R, glycogen as primer Zea mays
0.17
-
 ADP-glucose mutant enzyme K193E, glycogen as primer Zea mays
0.22
-
 ADP-glucose mutant enzyme K193E, amylopectin as primer Zea mays

Organism

Organism UniProt Comment Textmining
Zea mays
-
-
-

Purification (Commentary)

Purification (Comment) Organism
wild-type and mutant enzymes expressed in Escherichia coli Zea mays

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
ADP-glucose + amylopectin
-
 Zea mays ADP + ?
-
 ?
ADP-glucose + glycogen
-
 Zea mays ADP + ?
-
 ?

Synonyms

Synonyms Comment Organism
starch synthase IIa
-
 Zea mays