Biology Reference
In-Depth Information
Chapter 3
Phosphorylase-Catalyzed Enzymatic
Glycosylation
3.1
Fundamental Features of Phosphorylases
Various phosphorylases have been known, as summarized in Table
3.1, and all of them catalyze an exo-wise phosphorolysis of the
glycosidic linkage at the nonreducing end in the presence of an
inorganic phosphate (Fig. 3.1) [1,2]. The enzymes are named using
a combination of ''the name of the substrate and phosphorylase.''
The phosphorylases are generally classified by the anomeric forms
of the glycosidic linkages in the substrates that are phosphorolyzed
or by the anomeric forms of the glycose 1-phosphates that are
produced. The other way employed to classify phosphorylases is
describing them in terms of the anomeric retention or inversion in
the reaction. The stereo- and regiospecificities of phosphorylases
are very strict, and they catalyze the phosphorolysis of the specific
type of glycosidic linkages. The characteristics are important in
the exploitation of phosphorylases for the synthesis of oligo- and
polysaccharides with well-defined structure via the reverse reaction
of the phosphorolysis. Several phosphorylases can be employed
for the synthesis of polysaccharides or even oligosaccharides
with relatively high DPs, but other phosphorylases recognize only
disaccharide substrates and catalyze the reversible phosphorolysis
