Beta-Galactosidase (25 mg)
For Research Use Only
β-galactosidase is a hydrolase enzyme that catalyzes the hydrolysis of β-galactosides into monosaccharides. The protein comprises four chains and has a molecular weight of 464 kDa, each subunit with a weight of 116 kDa.
β-galactosidase is a commonly used reporter molecule and a very important marker for the lacZ gene. The enzyme can be split into two peptides; LacZα and LacZΩ. Neither is active by itself but both spontaneously reassemble into a functional enzyme. This characteristic is used in many cloning vectors to achieve a-complementation in specific laboratory strains of E. coli (the small LacZα peptide is encoded by the plasmid while the large LacZΩ is encoded in trans by the bacterial chromosome). When DNA fragments are inserted in the vector and production of LacZα disrupted, cells exhibit no β-galactosidase activity. This allows the blue/white screening of recombinant clones.
Specific activity is 230-375 Units/mg protein at 410 nm, pH 7.0 and 25°C (0.2 M Na-phosphate, 2 mM MgCl2, 8% methanol, 0.25% Tween 20). One unit of enzyme hydrolyses 1 micromole of ο-nitro-phenyl-β-D-galactopyranoside (ONPG) (46 mM) per minute. The protein concentration is assayed by the biuret method with BSA as standard. The free thiol groups on the enzyme surface are characterized to be 14-18 mole/mole enzyme. These free groups are useful for derivatisation of the enzyme.
One vial contains approximately 25 mg (8 KU) lyophilizate of partly purified enzyme. Reconstitution of this lyophilizate in 4 ml of water yields a solution of approximately 1 mM Tris-HCI, pH 7.2 and 1 mM MgCl2.For laboratory use only.
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High specific activity.
Hydrolysis of ß-galactosides into monosaccharides.
Supplied as lyophilized powder.
|Appearance: White lyophilized powder. |
Activity: 230-375 Units/mg protein at 410 nm, pH 7.0 and 25°C. (0.2 M Na-phosphate, 2mM MgCI2. 8% methanol, 0.25% Tween 20). One unit of enzyme hydrolyses 1 micromole of o-nitro-phenyl-β- D-galactopyranoside (ONPG) (46mM) per minute (the extinction coefficient for ONP at 410 nm is 2100 M/cm). The protein concentration is assayed by the biuret method with BSA as standard. The free thiol groups on the enzyme surface are characterized and are 14-18 mole/mole enzyme. The free thiol groups are useful for derivatisation of the enzyme.
|Reporter molecule. |
Blue/white screening of recombinant clones.
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