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International Journal of Marine Science 2013, Vol.3, No.37, 295-305
http://ijms.sophiapublisher.com
303
2.3 Hydroxyproline and collagen content
Estimation of the amino acid, hydroxyproline (Hyp) is
diagnostic of collagens in any organism. According to
our preliminary explorations of Hyp content in all the
collected sponges, six sponges along with
I. fusca
and
S. officinalis
possess high amount of Hyp than the
remaining sponges and the differences between these
selected sponges in their Hyp content was analyzed by
spectrophotometric method. However, specific important
has been given to
I. fusca
and
S. officinalis
to study
separately to emphasize on the collagenous network;
and four sponges considered for ultrastructural and
biochemical comparison in the present study. Collagen
content (based on Hyp concentration) significantly
differed in all the four experimental sponges. The
sponge,
C. fibrosa
seems to possess highest collagen
content (169.19 ± 9.12 mg/g freeze-dried sponge wt)
among all the four sponges (Table 3).
The solubility of collagens is a factor of extracting
different forms of collagen
viz.
, salt soluble (SS), acid
soluble (AS) and Insoluble (Ins). It is clear that the AS
and SS collagen content is not much varied but the
content of Ins collagen differed much among the four
sponges (Table 3). In all the sponges, the insoluble
(Ins) form of the collagen was more than the amount
of SS and AS forms of the collagen. Although the
total collagen content of
F. cavernosa
is less than
C.
fibrosa
and
H. cribriformis
, the collagen (Ins) is
higher (42.8±2.1 mg/g) when compared to other
sponges. However, the AS and SS collagen of
C.
fibrosa
is higher among all the experimental sponges.
3 Discussion
This is the first extensive work on the skeletal architecture,
isolation and characterization of collagens from
Demosponges available at Gulf of Mannar (GoM)
India. The GoM falls in the Indo-Pacific region, which
is considered one of the world's richest in marine
biological resources. It has more than 3600 species of
plants and animals that make it the biologically richest
coastal region in India (Kumaraguru et al., 2006).
Although the collected sponge species are localized to
specific habitat locations of GoM, there is much
variation in the morphology of each species due to the
seasonal changes and habitat disturbances by the local
trawlers. Since our studies mainly focus on the highly
important protein molecules like collagen,
Ircinia
fusca
was previously been well explored based on the
remarkable collagen like fiber content (Pallela et al.,
2011). While the general structural features of sponges
are visible through video microscopy, a more
elaborated picture on the presence of collagen was
obtained through electron microscopy. Gross and
Diehl-Seifert were the first to prove the existence of
collagen in marine as well as in freshwater sponges,
electron microscopically (Gross et al., 1956).
Furthermore, the orientation of spongin along with the
fine fibrillar material embedded in extra cellular
matrix of sponges is a major feature which forms the
basis of differentiation for the marine sponges.
Cowden (1970)
has
histologically proven the collagen
occurrence in marine sponge tissue. Besides this,
spongin skeleton formed of fine fibrils of collagen
interwoven along with other connective tissue
components like spicules and particulate matter could
be observed through SEM.
The macromolecules are the major constituents of
different forms of life and form the basis to determine
the structure of these life forms, to a certain extent.
The macromolecular content of different experimental
sponges was estimated to reach to the sponge species
with the highest amount of collagen as it is the main
structural component. It is well known that sponge
tissue protein content dominates other macromolecular
content ranging around 40% of the total dry tissue
weight (Hadas et al., 2005).
Except for hexoses,
C.
fibrosa
has shown higher collagen to relative protein,
pentose and lipid content than other sponge species.
Analysis of sponge biochemical components reveals
that not all the organic components were resolved in
the methods applied in the present research.
Collagen is the only intercellular organic framework
and amounts to approximately 10% of the total
organic matter in Demospongiae (Wiens et al., 1999).
Genomic and complementary DNA studies showed
that proteinaceous fibrous materials (collagen and
spongin) contain the classic collagenous Gly-Xaa-Yaa
motif (Exposito and Garrone, 1990; Boute et al.,
1996), where Hydroxyproline (Hyp) occupies any one
of the positions in the triplet motif other than Gly
(Glycine) position. Since the ultimate goal of the
project is to target the collagens, standard methods of
estimating Hyp to quantify collagen from marine
sponges was employed. Though it is a differential