Biomedical Engineering Reference
In-Depth Information
conduct an in-depth study of earthworm cellulase. Because of the abundance of
cellulose, it is promising to explore the purification methods and characteristics of
earthworm cellulase C
X
, an enzyme that can convert noncrystalline cellulose into
monosaccharides [
23
].
3.2.2.3
Ampullarum crossean
Ampullarum crossean
is also known as snails belonging to Mesogastropoda
Ampullariidae
Ampullarius
. It originates in the Amazon River basin in South
America, where people eat snails. It is delicious and has a large body and flesh;
is high in protein and low in fat; and has other characteristics.
Ampullarum
crossean
feeds on plants, grows rapidly, and contains many digestive enzymes,
especially cellulase with a high content and complete enzyme component
[
24
]. Cellulase separated from
A. crossean
contains three enzyme components:
endoglucanase, exoglucanase, and
-glucosidase. They can interrupt or loosen
cellulose chain separately, then hydrolyze the cellulose into dextrin cellulose,
cellotriose, cellobiose, and finally sugar and D-glucose [
25
]. Wang et al. purified
obtained a purified glucosidase from the gastric juice of herbivorous mollusks
A.
crossean,
which is ranked as the tenth in the glucosidase family. They also pointed
out that the enzyme is an endo-
“
“
-1,4-xylanase containing exo-
“
-1,4-glucanase
and endo-
-1,4-glucanase, called the multifunctional cellulase EGX. Thereafter,
gene encoding of the enzyme was cloned from the
A. crossean
genome and was
named egxa; it has a the full length of 1,683 bp, of which the encoded protein
is a multifunctional cellulase having a cellulose-binding domain and the catalytic
domain.
An internal multifunctional cellulase called EGX was isolated and purified from
the gastric juice of
A. crossean
with a molecular weight of 41.5 kDa. The cellulase
can hydrolyze denitrification of alkylphenol cellobioside (pNPC), microcrystalline
cellulose (MCC; Sigmacell), CMC, birch wood soluble xylan, oat spelt xylan, and
so on. It is a multifunctional cellulase with three enzyme activities: exo-
“
“
-1,4-
glucanases, endo-
-1,4-xylanase. After that,
the gene of the multifunctional cellulase was cloned from the
A. crossean
gene
group, named egxa. In the yeast expression system for methanol, recombinant
multifunctional cellulase EGXA is obtained that has a similar nature to EGX.
Amino acid sequence analysis showed that this enzyme belongs to the glycoside
hydrolase family 10 [
19
,
20
]. By comparison of the amino acid sequence of
multifunctional cellulase EGXA with dual-function cellulase (exo-
“
-1,4-glucanase enzymes, and endo-
“
-
1,4-xylanase C
ex
) from bacteria (
Cellulomonas fimi
), it was found that the homology
of multifunctional cellulase and EGXA with C
ex
reached 35 % [
26
].
In summary, the activity of cellulase from
A. crossean
is high, and it can digest
the yeast cell wall. The viscera of
A. crossean
are a good source for exploring the
enzyme system for cellulose degradation.
“
-1,4 cut of
“
