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Literature summary for 3.2.1.23 extracted from

  • Smart, J.; Richardson, B.
    Molecular properties and sensitivity to cations of beta-gaklactosidase from Streptomyces thermophilus with four enzyme substrates (1987), Appl. Microbiol. Biotechnol., 26, 177-185.
No PubMed abstract available

Inhibitors

Inhibitors Comment Organism Structure
D-galactose
-
Streptococcus thermophilus
Na+ competitive inhibitor of the Mg2+ and K+ activated reaction with either lactose or p-nitrophenyl-beta-D-galactoside Streptococcus thermophilus

KM Value [mM]

KM Value [mM] KM Value Maximum [mM] Substrate Comment Organism Structure
additional information
-
additional information effect of cations on the Km-value Streptococcus thermophilus
7
-
lactose in presence of 0.25 mM Mg2+, 50 mM K+ and 50 mM Na+ Streptococcus thermophilus
13
-
lactose in presence of 0.25 mM Mg2+ and 50 mM Na+ Streptococcus thermophilus
19
-
lactose in presence of 2 mM Mg2+ and 50 mM K+ Streptococcus thermophilus
26
-
lactose in presence of 0.25 mM Mg2+ and 50 mM K+ Streptococcus thermophilus
67
-
lactose in presence of 0.05 mM Mg2+ and 50 mM K+ Streptococcus thermophilus
138
-
lactose in presence of 0.25 mM Mg2+ Streptococcus thermophilus

Metals/Ions

Metals/Ions Comment Organism Structure
K+ synergistic activation with Mg2+ and Na+ or Mg2+ and K+. Na+ is the better activator with either o-nitrophenyl-D-galactoside or 4-methylumbelliferyl-beta-D-galactoside as substrates while K+ is the better activator of lactose and p-nitrophenyl-beta-D-galactoside Streptococcus thermophilus
Mg2+ synergistic activation with Mg2+ and Na+ or Mg2+ and K+. Na+ is the better activator with either o-nitrophenyl-D-galactoside or 4-methylumbelliferyl-beta-D-galactoside as substrates while K+ is the better activator of lactose and p-nitrophenyl-beta-D-galactoside Streptococcus thermophilus
Na+ synergistic activation with Mg2+ and Na+ or Mg2+ and K+. Na+ is the better activator with either o-nitrophenyl-D-galactoside or 4-methylumbelliferyl-beta-D-galactoside as substrates while K+ is the better activator of lactose and p-nitrophenyl-beta-D-galactoside Streptococcus thermophilus

Molecular Weight [Da]

Molecular Weight [Da] Molecular Weight Maximum [Da] Comment Organism
116000
-
x * 116000, SDS-PAGE Streptococcus thermophilus
186000
-
enzyme form A2, gel filtration Streptococcus thermophilus
204000
-
enzyme form A1, gel filtration Streptococcus thermophilus
282000
-
enzyme form B1, gel filtration Streptococcus thermophilus

Organism

Organism UniProt Comment Textmining
Streptococcus thermophilus
-
-
-

Purification (Commentary)

Purification (Comment) Organism
enzyme form A1, A2, and B1 Streptococcus thermophilus

Specific Activity [micromol/min/mg]

Specific Activity Minimum [µmol/min/mg] Specific Activity Maximum [µmol/min/mg] Comment Organism
466
-
-
Streptococcus thermophilus

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
4-methylumbelliferyl-beta-D-galactoside + H2O
-
Streptococcus thermophilus 4-methylumbelliferone + beta-D-galactose
-
?
lactose + H2O
-
Streptococcus thermophilus D-glucose + D-galactose
-
?
o-nitrophenyl-beta-D-galactoside + H2O
-
Streptococcus thermophilus o-nitrophenol + beta-D-galactose
-
?
p-nitrophenyl-beta-D-galactoside + H2O
-
Streptococcus thermophilus p-nitrophenol + beta-D-galactose
-
?

Subunits

Subunits Comment Organism
? x * 116000, SDS-PAGE Streptococcus thermophilus