Hall B G, Reeve E C
J Bacteriol. 1977 Oct;132(1):219-23. doi: 10.1128/jb.132.1.219-223.1977.
Klebsiella strain RE1544 contains two lac operons, one on the chromosome and one on a lac plasmid. A mutant of RE1544, in which the lacZ genes of both operons produce no active enzyme, was found to synthesize a beta-galactosidase that hydrolyzes ortho-nitrophenyl-beta-D-galactopyranoside but not lactose. Synthesis of this beta-galactosidase (BGase-III) is induced by lactose but not by isopropyl-1-thio-beta-D-galactopyranoside or methyl-beta-D-thiogalactopyranoside. In both the regulation of synthesis and substrate specificity, BGase-III strongly resembles the ebg0 enzyme of Escherichia coli. Nevertheless, by the criteria of immunological cross-reactivity and subunit molecular weight, BGase-III is not related to the ebg0 enzyme.
肺炎克雷伯菌菌株RE1544含有两个乳糖操纵子，一个在染色体上，另一个在乳糖质粒上。发现RE1544的一个突变体，其中两个操纵子的lacZ基因均不产生活性酶，该突变体可合成一种β-半乳糖苷酶，它能水解邻硝基苯基-β-D-吡喃半乳糖苷，但不能水解乳糖。这种β-半乳糖苷酶（BGase-III）的合成由乳糖诱导，而不由异丙基-1-硫代-β-D-吡喃半乳糖苷或甲基-β-D-硫代吡喃半乳糖苷诱导。在合成调节和底物特异性方面，BGase-III与大肠杆菌的ebg0酶非常相似。然而，根据免疫交叉反应性和亚基分子量的标准，BGase-III与ebg0酶无关。
