SUMMARY: 3A fragments of (NCIB 10682) DNA were ligated into the HI site of pBR322 and expressed in HB101 and a Lac mutant thereof. Twenty-eight clones with carboxymethylcellulase (CMCase) activity were selected from two libraries by means of the Congo Red plate assay. Restriction enzyme analysis indicated that the CMCase clones contained a total of 13 unique DNA inserts. Hybridization of recombinant plasmids with chromosomal DNA confirmed the physical maps in all but one case and was further used to demonstrate the absence of homology between the dlll restriction fragments of similar size which occurred in many of the clones. Without exception, CMCase clones expressed endoglucanase activity, but differed with respect to the amount and nature of the enzyme activity produced; additionally, some clones had exoglucanase activty which, in at least one case, was not attributable to the production of a second enzyme. For a few selected clones, the partially purified CMCase was analysed by electrophoresis. A temperature profile characteristic of a thermostable enzyme was demonstrated for the endoglucanase of one of the most active clones. Based on the evidence presented here, it is probable that the 13 unique DNA fragments described do not contain any of the endoglucanase genes previously cloned.


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