Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Carboxymethylated beta-galactosidase from Escherichia coli was dissociated at 100 degrees C to form carboxymethylated fragments A and B. The mol.wts. of carboxymethylated fragments A and B were determined by gel filtration to be 64300 and 22400 respectively. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis of carboxymethylated fragments A and B that had been pretreated with 2-mercaptoethanol and sodium dodecyl sulphate yielded mol.wts. of 64000 and 22100 respectively. Carboxymethylated fragments A and B had arginine as their C-terminal amino acid. When a crude extract of E. coli M15 was filtered through a column of Sepharose 6B, it was found that carboxymethylated fragment B could restore beta-galactosidase activity when added to fractions having mol.wts. estimated to be 123000, 262000 and 506000. These fractions are referred to as ;complementable fractions'. Similarly, it was found that carboxymethylated fragment A could restore enzyme activity to tractions having mol.wts. estimated to be 63000, 253000 and 506000. Estimates of the molecular weights of the beta-galactosidase activity obtained by restoration with carboxymethylated fragments A and B were made by filtering the active enzyme through another column of Sepharose 6B. The enzyme obtained by complementation with carboxymethylated fragment B, i.e. the complemented enzyme, had mol.wt. 525000, and that obtained with carboxymethylated fragment A had mol.wts. of 525000, 646000 and 2000000. The latter finding suggests that multiple forms of complemented beta-galactosidase can exist.
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PMID:Restoration of beta-galactosidase to Escherichia coli M15. Complementation studies. 41 87

1. Two "acid" forms, Am and Al, of beta-galactosidase from sheep kidney have been isolated and purified 349- and 154-fold, respectively, with a recovery of about 8%. 2. Their mol. wts were about 450,000 and 230,000, respectively. Am seems to be a dimer of Al. The aggregation is stimulated by NaCl. 3. The "acid" beta-galactosidase has a pH optimum between 4.0 and 5.0 for both forms. They are located in the lysosomes. The optimal temperature is 37 degrees C and 40 degrees C for Al and Am forms, respectively. 4. Three peaks were detected by isoelectric focusing. After sialidase treatment, these peaks were obtained at higher pH values. 5. The activation energy values were 10.75 and 11.72 kcal/mol for Am and Al, respectively. 6. A variety of chemicals were tested as possible activators or inhibitors. The enzyme is strongly inhibited by gamma-D-galactonolactone, and the kinetic evidence suggests a competitive inhibition in all cases.
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PMID:Purification and characterization of different "acid" beta-galactosidases from sheep kidney. 176 16

Plasmids were constructed which carry two, three or four active lacZ genes of Escherichia coli fused head-to-tail in phase. The products of these oligomeric lacZ genes are shown to be polypeptides with expected subunit mol. wts. of 230 kd (di-beta-galactosidase), 350 kd (tri-beta-galactosidase) and 460 kd (tetra-beta-galactosidase). Di-beta-galactosidase has the same enzymatic activity as the wild-type enzyme. It subunits are practically not degraded proteolytically in vivo. It aggregates predominantly to a dimer which has the same sedimentation constant as the wild-type tetrameric enzyme. Furthermore, it is more heat stable than the wild-type enzyme. Tri- and tetra-beta-galactosidase have strongly reduced enzymatic activities and are largely degraded. Our experiments lead us to propose that covalent joining of two subunits through proper gene duplication may possibly be an intermediate in the evolution of self aggregation of homo-oligomeric proteins.
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PMID:Fused lacZ genes code for di-, tri- and tetra-beta-galactosidase in Escherichia coli. 392 88

1. A beta-galactosidase was purified ca 245-fold to homogeneity from Penaeus monodon, with a final spec. act. of 61.3 U/mg of protein. 2.By using SDS-polyacrylamide gel electrophoresis, the monomers of shrimp beta-galactosidase were discovered to have mol. wts of 31,000 and those of human placental enzyme, 32,000. Since the active shrimp beta-galactosidase was found to have a mol. wt of 66,000 by AcA 34 gel filtration chromatography,it was concluded that the purified shrimp enzyme was dimeric. 3.In contrast to the discovery of thermostability with human placental beta-galactosidase, the shrimp enzyme was found to be unstable to heating at 45 degree C for 10 min. Both enzyme activities were inhibited by Mn (2+) and Zn (2+) ions.4. The shrimp beta-galactosidase has an isoelectric point (pI) of 7.0, but the human placental enzyme has a pI of 5.5. Both enzymes were sialyated. 5.The shrimp beta-galactosidase has a pH optimum at 7.0 and its K(m) was 1.9 micrometer with 4-methylumbelliferyl-beta-D-galactoside as substrate. The human enzyme has pH optimum at 7.0 or 4.0, and its K(m) was 9.8 micrometer.
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PMID:A neutral beta-galactosidase from the hepatopancreas of the shrimp Penaeus monodon (Crustacea: Decapoda): dimeric and sialyated. 2050 8