Enzymatic hydrolysis was monitored in real-time using time dependent static
light scattering (TDSLS) for a variety of galactomannans from native Brazi
lian flora. alpha -Galactosidase, which strips only the (1-6)alpha -D galac
tose side groups, and beta -mannanase, which hydrolyses only the (1-4)beta
-D mannan main chain into oligosaccharides were investigated separately and
in combination. The time-dependent signatures matched those describing sid
e-chain stripping for galactosidase, whereas those resulting from the actio
n of mannanase followed the signature typical of random backbone cleavage.
Use of both enzymes together required that the TDSLS theory of polymer degr
adation be extended to the case where random backbone cleavage sites appear
as side chains are stripped by the first enzyme. Whereas galactosidase all
owed mannanase to access more backbone cleavage sites as time passes, leadi
ng to a higher degree of hydrolysis, there was no increase in rate constant
s. The distribution of random fragments in the case of mannanase digestion
alone followed reasonably well the predictions for random cleavage of a sin
gle-strand polymer with a restricted number of cleavage sites. The fragment
distributions were evaluated by size exclusion chromatography. (C) 2001 Jo
hn Wiley & Sons. Inc.