W. Hashimoto et al., Characterization of alpha-L-rhamnosidase of Bacillus sp GL1 responsible for the complete depolymerization of gellan, ARCH BIOCH, 368(1), 1999, pp. 56-60
A bacterium, Bacillus sp. GL1, depolymerizes a heteropolysaccharide (gellan
) to a tetrasaccharide (unsaturated glucuronyl-glucosyl-rhamnosyl-glucose)
by extracellular gellan lyase. The resultant tetrasaccharide was degraded t
o the constituent monosaccharides by subsequent reactions of unsaturated gl
ucuronyl hydrolase, beta-D-glucosidase, and alpha-L-rhamnosidase. alpha-L-R
hamnosidase was substantially induced in the bacterial cells when grown in
a medium containing gellan as a carbon source. The purified enzyme from the
cells was a monomer with a molecular mass of about 100 kDa and was most ac
tive at pH 7.0 and 50 degrees C. The enzyme acted on the gellan-degrading p
roduct (rhamnosyl-glucose) formed after successive reactions catalyzed by g
ellan lyase, unsaturated-glucuronyl hydrolase and beta-D-glucosidase, and r
eleased rhamnose from the disaccharide. Therefore, the alpha-L-rhamnosidase
is found to be responsible as the final enzyme for the complete depolymeri
zation of gellan. (C) 1999 Academic Press.