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The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
H P Zhang – 1st expert on this subject based on the ideXlab platform
Immobilization of recombinant thermostable Beta–Galactosidase from Bacillus stearothermophilus for lactose hydrolysis in milk.Journal of dairy science, 2009Co-Authors: W. Chen, Harry Chen, Y. Xia, J Yang, J. Zhao, F. Tian, H P ZhangAbstract:
A recombinant thermostable Beta–Galactosidase from Bacillus stearothermophilus was immobilized onto chitosan using Tris(hydroxymethyl)phosphine (THP) and glutaraldehyde, and a packed bed reactor was utilized to hydrolyze lactose in milk. The thermostability and enzyme activity of THP-immobilized Beta–Galactosidase during storage was superior to that of free and glutaraldehyde-immobilized enzymes. The THP-immobilized Beta–Galactosidase showed greater relative activity in the presence of Ca(2+) than the free enzyme and was stable during the storage at 4 degrees C for 6 wk, whereas the free enzyme lost 31% of the initial activity under the same storage conditions. More than 80% of lactose hydrolysis in milk was achieved after 2 h of operation in the reactor. Therefore, THP-immobilized recombinant thermostable Beta–Galactosidase from Bacillus stearothermophilus has the potential for application in the production of lactose-hydrolyzed milk.
Yakov Gluzman – 2nd expert on this subject based on the ideXlab platform
Beta Galactosidase containing a human immunodeficiency virus protease cleavage site is cleaved and inactivated by human immunodeficiency virus proteaseProceedings of the National Academy of Sciences of the United States of America, 1990Co-Authors: Ellen Z Baum, Geraldine A Bebernitz, Yakov GluzmanAbstract:
A “cleavage cassette” specifying a decapeptide human immunodeficiency virus (HIV) protease cleavage site was introduced into six different locations of Beta–Galactosidase (Beta-D-galactoside galactohydrolase, EC 184.108.40.206) in Escherichia coli. Four of these constructs retained Beta–Galactosidase activity despite the insertion of the cleavage cassette. Of these four constructs, one was cleaved by HIV protease, resulting in the inactivation of Beta–Galactosidase both in vivo and in vitro. This cleavage was inhibited by pepstatin A, a known inhibitor of HIV protease. Thus, Beta–Galactosidase has been converted into an easily assayed substrate for HIV protease. An analogous construct of Beta–Galactosidase containing a polio protease cleavage site was cleaved likewise by polio protease, suggesting that this system may be generic for monitoring cleavage by a variety of proteases.
Randy Schekman – 3rd expert on this subject based on the ideXlab platform
Invertase Beta–Galactosidase hybrid proteins fail to be transported from the endoplasmic reticulum in Saccharomyces cerevisiae.Molecular and Cellular Biology, 2015Co-Authors: Scott D. Emr, I Schauer, W Hansen, P Esmon, Randy SchekmanAbstract:
The yeast SUC2 gene codes for the secreted enzyme invertase. A series of 16 different-sized gene fusions have been constructed between this yeast gene and the Escherichia coli lacZ gene, which codes for the cytoplasmic enzyme Beta–Galactosidase. Various amounts of SUC2 NH2-terminal coding sequence have been fused in frame to a constant COOH-terminal coding segment of the lacZ gene, resulting in the synthesis of hybrid invertase-Beta–Galactosidase proteins in Saccharomyces cerevisiae. The hybrid proteins exhibit Beta–Galactosidase activity, and they are recognized specifically by antisera directed against either invertase or Beta–Galactosidase. Expression of Beta–Galactosidase activity is regulated in a manner similar to that observed for invertase activity expressed from a wild-type SUC2 gene: repressed in high-glucose medium and derepressed in low-glucose medium. Unlike wild-type invertase, however, the invertase-Beta–Galactosidase hybrid proteins are not secreted. Rather, they appear to remain trapped at a very early stage of secretory protein transit: insertion into the endoplasmic reticulum (ER). The hybrid proteins appear only to have undergone core glycosylation, an ER process, and do not receive the additional glycosyl modifications that take place in the Golgi complex. Even those hybrid proteins containing only a short segment of invertase sequences at the NH2 terminus are glycosylated, suggesting that no extensive folding of the invertase polypeptide is required before initiation of transmembrane transfer. Beta–Galactosidase activity expressed by the SUC2-lacZ gene fusions cofractionates on Percoll density gradients with ER marker enzymes and not with other organelles. In addition, the hybrid proteins are not accessible to cell-surface labeling by 125I. Accumulation of the invertase-Beta–Galactosidase hybrid proteins within the ER does not appear to confer a growth-defective phenotype to yeast cells. In this location, however, the hybrid proteins and the Beta–Galactosidase activity they exhibit could provide a useful biochemical tag for yeast ER membranes.