Ms. Ekinci et al., ISOLATION AND OVEREXPRESSION OF A GENE ENCODING AN EXTRACELLULAR BETA-(1,3-1,4)-GLUCANASE FROM STREPTOCOCCUS-BOVIS JB1, Applied and environmental microbiology, 63(10), 1997, pp. 3752-3756
Streptococcus bovis JB1 was found to produce a 25-kDa extracellular en
zyme active against beta-(1,3-1,4)-glucans. A gene was isolated encodi
ng a specific beta-(1,3-1,4)-glucanase that corresponds to this size a
nd belongs to glycoside hydrolase family 16. A 4- to 10-fold increase
in supernatant beta-glucanase activity was obtained when the cloned be
ta-glucanase gene was reintroduced into S, bovis JB1 by use of constru
cts based on the plasmid vector pTRW10 or pIL253, The beta-(1,3-1,4)-g
lucanase gene was also expressed upon introduction of the pTRW10 const
ruct pTRWL1R into Lactococcus lactis IL2661 and Enterococcus faecalis
JH2-SSI although extracellular activity was 8- to 50-fold lower than t
hat in S. bovis JB1. The beta-(1,3-1,4)-glucanase purified from the cu
lture supernatant of S. bovis JB1 carrying pTRWL1R showed a K-m of 2.8
mg per mi and a V-max of 338 mu mol of glucose equivalents per min pe
r mg of protein with barley beta-glucan as the substrate. The S, bovis
beta-(1,3-1,4)-glucanase may contribute to the ability of this bacter
ium to utilize starch by degrading structural polysaccharides present
in endosperm cell walls.