Chemistry Reference
In-Depth Information
heparin and HS, or bacterial chondroitinases and mammal hyalur-
onidases, active on both CS and HA. Nevertheless, chondroitinases are
not hydrolases but eliminases (lyases) leading to degradation products
containing an unsaturated hexuronic acid at the non-reducing end. On
the other hand, hyaluronidases are hydrolases but are not suitable for the
production of CS oligosaccharides because of their low throughput on
the CS polysaccharides. Therefore, there is a need to find new enzymes
and/or new processes leading to well-defined oligosaccharides in high
yields and without side-reactions such as elimination, desulphation or
deacetylation. In 2010, Hehemann et al. isolated and characterized the
first b-porphyranase inactive on standard agarose ([4)-3,6-An-a-
L
-Gal-(1
-
3)-b-
D
-Gal-(1
]
n
), but highly specific to porphyran, which possesses a
highly substituted and sulphated agarose backbone (ideally consisting of
[3)-b-Gal-(1
-
]
n
).
96
In 2011, the same group applied
this discovery to the degradation of porphyran from P. umbilicalis using
the recombinant b-porphyranase A and compared it to b-agarase B.
97
While agarase produces predominantly non-sulphated oligosaccharides,
b-porphyranase A produced oligosaccharides of the a-
L
-Gal-6S-(1
-
4)-a-
L
-Gal-6-S-(1
-
3)-b-
D
-
Gal series centred on DP 2, 4 or 6 after size-exclusion chromatography.
Huang et al. isolated a new alginate lyase which possesses a different
endolytic reaction mode from other unknown alginate lyases.
98
More-
over, this enzyme prefers poly-a-
L
-guluronate as a substrate over poly-b-
D
-
mannuronate. Degradation of sodium alginate using this newly isolated
enzyme led to high yields of oligoguluronates with DP 5, 6 and 7. More
''exotic'' enzymes were also tested to produce anionic oligosaccharides.
For example, endoxylanase from Streptomyces sp. was used for degrad-
ation of kenaf xylan.
99
The main chain of this polysaccharide consists of
xyloses residues, some of which carry 4-O-Me-GlcA and GlcA as side
chains and some studies confirmed that GalA is also present. After
fractionation by anion exchange chromatography, neutral xylo-
oligosaccharides but also seven acidic oligosaccharides consisting of Xyl,
4-O-Me-GlcA, GlcA and GalA residues were obtained. Finally, some new
processes for enzymatic depolymerisation were also tried. In particular,
for the fast (one step) production and characterization of OGA from PGA,
Delattre et al. proposed an enzymatic bioreactor using Convective Inter-
action Media Disk (CIM-disk) supports.
100
CIM monolithic supports is a
novel generation of stationary phase used for liquid chromatography and
bioconversion. The immobilization of the pectin lyase presents a lot of
advantages as high stability and reusability. Moreover, the CIM-disks are
ecient chromatographic supports. After incubation and purification by
HPLC (DEAE), OGA with DP up to 5 were obtained, and the CIM-disk
system can be reused up to 10 times with no significant decrease in the
eciency.
-
4 Applications
Due to their fine structure, their conformation and charge, anionic
oligosaccharides have a wild range of biological activities of interest.
They are very important molecules like their polysaccharide counterparts
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