Biomedical subjects

O Shoseyov

Publications and source records attributed to O Shoseyov.

21 records · Page 2Linked to original sources

PubMed1990

Cloning of Clostridium cellulovorans endo-1,4-beta-glucanase genes.

A Clostridium cellulovorans lambda gt11 gene bank was screened for endo-1,4-beta-glucanase [EC 3.2.1.4, EGase, Carboxy Methyl Cellulase (CMCase)] genes using a chromogenic substrate. Three genes (engA, engB, and engC) were isolated. The engB expressed the most active CMCase. The engA encoded a bifunctional enzyme that displayed endo-1,4-beta-glucanase and beta-glucosidase activities. The three recombinant glucanases, when expressed in Escherichia coli, were partially degraded into multiform active enzymes as evidenced by their SDS-PAGE-CMC zymograms. None of the clones could degrade crystalline cellulose, thus supporting the hypothesis that the integrity of the C. cellulovorans cellulase complex was essential for its 'true cellulase' activity.

Cellulase↗

PubMed1990

Multiple active forms of a novel serine protease from Bacillus subtilis.

We have cloned and sequenced a gene (epr) encoding a novel serine protease from Bacillus subtilis. Several active forms of the enzyme with molecular masses between 40 and 34 kDa were found in the medium of B. subtilis cultures containing the epr gene cloned on a plasmid. Deletions at the 3' end of the gene, removing up to 240 amino acids of the reading frame, abolished the expression of the larger species but did not affect the expression of the 34 kDa enzyme. The C-terminal third of the protein is therefore not required for protease activity. The size variation of the active forms expressed by the complete epr gene appears to be the result of partial removal of the C-terminus either by processing or degradation. Thus, the epr gene consists of two domains, one encoding a serine protease homologous to subtilisin and the other a C-terminus of unknown function.

Amino Acid Sequence↗

PubMed1990

Essential 170-kDa subunit for degradation of crystalline cellulose by Clostridium cellulovorans cellulase.

The cellulase complex from Clostridium cellulovorans has been purified and its subunit composition determined. The complex exhibits cellulase activity against crystalline cellulose as well as carboxymethylcellulase (CMCase) and cellobiohydrolase activities. Three major subunits are present with molecular masses of 170, 100, and 70 kDa. The 100-kDa subunit is the major CMCase, although at least four other, minor subunits show CMCase activity. The 170-kDa subunit has the highest affinity for cellulose, does not have detectable enzymatic activity, but is necessary for cellulase activity. Immunological studies indicate that the 170-kDa subunit is not required for binding of the catalytic subunits to cellulose and therefore does not function solely as an anchor protein. Thus this core subunit must have multiple functions. We propose a working hypothesis that the binding of the 170-kDa subunit converts the crystalline cellulose to a form that is capable of being hydrolyzed in a cooperative fashion by the associated catalytic subunits.

Cellulase↗