Thermal Inactivation Kinetics of Escherichia coli .BETA.-Galactosidase.

The beta-d-galactosidase of Escherichia coli, strain K-12.

Regulation of enzymatic activity in the intact cell: the beta-D-galactosidase of Escherichia coli.

Large differences in enzymatic activity are often found between intact cells and extracts. Lacking a better explanation, it has frequently been assumed that the penetration of the substrate is the rate limiting step in the intact cells. The experiments reported here were designed to test several hypotheses which might account for the discrepancy. The 3-galactosidase (lactase) in Escherichia col...

Derepression of beta-galactosidase synthesis in Escherichia coli K-12 by p-fluorophenylalanine.

p-Fluorophenylalanine (FPA) derepresses beta-galactosidase synthesis at 35 C but not at 25 C in Escherichia coli K-12, strain MC132 (lac I1,2), a strain with a temperature-sensitive lac repressor. In contrast, strain MC130 (lac I(+)) is not derepressed by FPA at 35 C. Temperature-shift experiments with strain MC132 in the presence of FPA and other reagents (isopropyl-1-thio-beta-d-galactoside o...

Cloning and expression of the beta-D-galactosidase gene from Streptococcus thermophilus in Escherichia coli.

The beta-D-galactosidase (beta-gal) gene from Streptococcus thermophilus was cloned to isolate and characterize it for potential use as a selection marker in a food-grade cloning vector. Chromosomal DNA from S. thermophilus 19258 was cleaved with the restriction enzyme PstI and ligated to pBR322 for transformation into Escherichia coli JM108. A beta-galactosidase-positive clone was detected by ...

Inhibition of beta-galactosidase biosynthesis in Escherichia coli by tetracycline residues in milk.

Low levels of tetracyclines found as residues in milk inhibited the biosynthesis of beta-galactosidase in Escherichia coli. To produce the same effect, other antibacterials had to occur in concentrations that were more than 10-fold higher. This relative selectivity was exploited for the development of a screening test for tetracyclines in milk based on a chemiluminometric assay of beta-galactos...