Abstract
SEVERAL studies have shown that the intestinal mucosa of various mammals contains at least two β-galactosidases1–5. One of these has a primary specificity for lactose; the other has a primary specificity for synthetic β-galactosides such as o-Nitrophenyl β-D-galactopyranoside (ONPG). Since strains of Escherichia coli K12 bearing deletions of the lac Z gene have a very small residual activity toward ONPG, there must also be a second β-galactosidase in E. coli. We report here that E. coli K12 does indeed possess a second β-galactosidase. Although this enzyme has virtually no activity toward lactose, its synthesis is induced by lactose.
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HARTL, D., HALL, B. Second naturally occurring β-galactosidase in E. coli. Nature 248, 152–153 (1974). https://doi.org/10.1038/248152a0
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DOI: https://doi.org/10.1038/248152a0
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