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amino acids stabilize the transition state. Most cellulases, xylanases and
lysozyme seem to be hydrolases, but see c) below.
b) Lyases
Alginate lyases are enzymes that work by the same mechanism as does
alkaline
β
-elimination, and has therefore the same reaction product (4,5
unsaturated uronic acid).
c) Lytic monooxygenases
Recently (2013) a new and exciting type of polysaccharide-degrading
enzymes have been discovered which are collectively named ‘lytic
monooxygenases’. Of these enzymes, the cellulose degrading types are
particular promising because they may possibly be developed into powerful
reagents in the quest to transform wood into ethanol and thereby avoiding
using foods for the same purpose.
The enzymes catalyse a reaction between polysaccharides and molecular
oxygen (O
2
) which leads to chain break and the formation of a lactone at the
reducing end:
The lactone (cyclic ester, compare to GDL, Section 1.2.20) may hydrolyse,
especially under alkaline conditions, to form the corresponding carboxylic
acid.
OH
O
HOH
2
C
OH
HO
O
O
HO
HO
O
OH
O
HOH
2
C
OH
HO
O
O
HOH
2
C
HO
+ O
2
Lytic monooxygenase
OH
O
HOH
2
C
OH
HO
O
O
HO
HO
HO
OH
O
HOH
2
C
OH
HO
O
O
HOH
2
C
HO
O
OH
O
HOH
2
C
OH
HO
O
OH
HO
HO
O
OH