12.2 Occurrence in Nature
263
1979). Without collagen, bone will be completely brittle and without the bone minerals, bone would have no rigidity. Therefore, the combination of collagen and minerals
gives bone the ideal mechanical property to perform its biological function.
Collagen plays a structural role in the extracellular matrix where it provides thermal and mechanical stability as well as interaction with the surrounding cells and
components. Collagen can be of several types mainly type I and type II collagen,
although there are up to 28 different types of collagen in vertebrates on land and in
water (Shoulders and Raines 2009). Type I collagen consists of two alpha-1-chains
and one alpha-2-chains in the triple helix structure (Felician et al. 2019). Type I collagen is more abundant in marine invertebrates such as sea urchins, jellyfish, starfish
and squids (Benedetto et al. 2014; Tan et al. 2013; Delphi et al. 2016). Collagens
from fish parts such as scales, fins, skin and bones have been mostly identified as
type 1 collagen. Since human collagen is about 90% type 1 collagen fish sourced
collagen has the potential to have good compatibility with the human system when
used externally or internally. Whale sharks collagen is type II collagen (Jeevithan
et al. 2015). Collagen is distinct from other proteins by their right-handed triple helix
structure as well as the occurrence of the amino acid glycine at every third residue
along the polypeptide chain.
12.3 Chemistry of Collagens
The general structure of collagen is a right-handed triple helix structure. A fibrous
protein does not have a tertiary structure as this helix structure does not fold up.
Collagen has high molecular weight. For example, collagen extracted from the jellyfish Rhopilema esculentum had a molecular weight of between 100 and 150 kDa
when measured using sodium dodecyl sulfate-polyacrylamide gel electrophoresis
(SDS-PAGE) and Fourier transform infrared (FTIR) (Felician et al. 2019). This was
then broken down with enzymes to polypeptides with 10–15 kDa and then further
reduced to 25 kDa with further enzyme treatment. Different types of enzyme break
different types of bonds such that the molecular weight of the proteins can be varied
by varying the enzyme used. The molecular weight has an impact on the bioactivity
of collagen (Chi et al. 2014); therefore, the ability to modify the molecular weight
of collagen increases the diversity of their applications (Fig. 12.1).
In fish collagen which could be obtained from the skin, fins or scales, alanine and
glycine were most abundant in the stated order, while tryptophan was not present
in the collagen structure (Mahboob 2015). The other more prominent amino acids
that occur on the collagen polypeptide chains are proline and hydroxyproline. There
are cases where the polypeptides making up the collagen triple helix are identical
polymeric chains made up of the same amino acid repeating units, and this is referred
to as homotrimeric triple helix. It is however more common to have the case where
the polypeptides are not identical polymer chains; this is referred to as heterotrimeric.
263
1979). Without collagen, bone will be completely brittle and without the bone minerals, bone would have no rigidity. Therefore, the combination of collagen and minerals
gives bone the ideal mechanical property to perform its biological function.
Collagen plays a structural role in the extracellular matrix where it provides thermal and mechanical stability as well as interaction with the surrounding cells and
components. Collagen can be of several types mainly type I and type II collagen,
although there are up to 28 different types of collagen in vertebrates on land and in
water (Shoulders and Raines 2009). Type I collagen consists of two alpha-1-chains
and one alpha-2-chains in the triple helix structure (Felician et al. 2019). Type I collagen is more abundant in marine invertebrates such as sea urchins, jellyfish, starfish
and squids (Benedetto et al. 2014; Tan et al. 2013; Delphi et al. 2016). Collagens
from fish parts such as scales, fins, skin and bones have been mostly identified as
type 1 collagen. Since human collagen is about 90% type 1 collagen fish sourced
collagen has the potential to have good compatibility with the human system when
used externally or internally. Whale sharks collagen is type II collagen (Jeevithan
et al. 2015). Collagen is distinct from other proteins by their right-handed triple helix
structure as well as the occurrence of the amino acid glycine at every third residue
along the polypeptide chain.
12.3 Chemistry of Collagens
The general structure of collagen is a right-handed triple helix structure. A fibrous
protein does not have a tertiary structure as this helix structure does not fold up.
Collagen has high molecular weight. For example, collagen extracted from the jellyfish Rhopilema esculentum had a molecular weight of between 100 and 150 kDa
when measured using sodium dodecyl sulfate-polyacrylamide gel electrophoresis
(SDS-PAGE) and Fourier transform infrared (FTIR) (Felician et al. 2019). This was
then broken down with enzymes to polypeptides with 10–15 kDa and then further
reduced to 25 kDa with further enzyme treatment. Different types of enzyme break
different types of bonds such that the molecular weight of the proteins can be varied
by varying the enzyme used. The molecular weight has an impact on the bioactivity
of collagen (Chi et al. 2014); therefore, the ability to modify the molecular weight
of collagen increases the diversity of their applications (Fig. 12.1).
In fish collagen which could be obtained from the skin, fins or scales, alanine and
glycine were most abundant in the stated order, while tryptophan was not present
in the collagen structure (Mahboob 2015). The other more prominent amino acids
that occur on the collagen polypeptide chains are proline and hydroxyproline. There
are cases where the polypeptides making up the collagen triple helix are identical
polymeric chains made up of the same amino acid repeating units, and this is referred
to as homotrimeric triple helix. It is however more common to have the case where
the polypeptides are not identical polymer chains; this is referred to as heterotrimeric.