214
10 Aquatic Plants and Algae Proteins
whose repeating units can be trillions of variations of arrangements of 20 different
amino units. Unlike other aquatic polymers that have been explored in this book
such as fucoidans and carrageenans, proteins are monodisperse; they have uniform
molecular weight, hence number of repeating units within their polymer chains.
Proteins differ from one another by the sequences of amino acids in their primary
structure, the interaction of the polypeptide chain in the secondary structure and the
folding of these chains in the tertiary structure. Some proteins further have a quaternary structure defined by the combination of different folded polypeptide structures
by hydrogen bonds. One such protein with a quaternary structure is hemoglobin.
Some researchers have explored how to develop other monodisperse polyamides
from proteins as a route to achieving monodispersity in polymerization reactions
(Yang et al. 2003).
Some proteins from aquatic organisms share the same general chemistry as proteins from terrestrial organisms. Proteins such as collagen, luciferase and amylase
are examples of proteins found in land as well as aquatic organisms. However, some
of these proteins have some distinct features in terms of their chemical structure that
differs from one another. The rest of this section will highlight some of the features
specific to aquatic proteins.
Despite some of the adverse effects associated with the consumption of high
quantity of meat, animal protein has the highest amount of all essential amino acids
required for healthy nutrition for humans. To counter the risks associated with meat
consumption such as high fat content leading to cardiovascular disease, it is recommended to consume a diet consisting of mainly plant-based proteins and achieve
the required essential amino acids through a combination of a range of plant protein
sources such as legumes, grains, fruits and vegetables (FAO, WHO 1991).
Despite being considered as highly nutritious consisting of proteins, vitamins and
minerals, amino acid composition of algae is rather limited. Some of the essential
proteins, which are not synthesized by humans and required by the body, are not
present in algae. This is the general case with plant protein, whereby some essential
amino acids are missing in plants of both terrestrial and aquatic. These essential
amino acids missing in plants include leucine, histidine, tryptophan, lysine, valine,
threonine, methionine and phenylalanine (Young and Pellett 1994). The amino acid
missing in particular plant or algae varies from species to species. For example, in
red algae, leucine and isoleucine are usually present in low amounts in brown algae
cysteine, while lysine and methionine are the missing or limited amino acids in brown
algae. Tryptophan and lysine are generally in limited amounts in all algae (Bleakley
and Hayes 2017). Amino acids which are more abundant in algae include aspartic
acid and glutamic acid which could be up to 22–44% in species Fucus sp. and up to
32% in Ulva sp. (Fleurence 1999).
While algae and aquatic plants cannot serve as a main source of proteins due
to the absence of some essential amino acids, they nonetheless can serve as an
additional more efficient protein source. Polypeptides from plant sources tend to be
cyclic peptides, and these are known to have more bioactive properties than the linear
structures. The cyclic structures tend to be more stable than the linear structures (Tan
and Zhou 2006). This stability could ensure they retain their secondary structure
10 Aquatic Plants and Algae Proteins
whose repeating units can be trillions of variations of arrangements of 20 different
amino units. Unlike other aquatic polymers that have been explored in this book
such as fucoidans and carrageenans, proteins are monodisperse; they have uniform
molecular weight, hence number of repeating units within their polymer chains.
Proteins differ from one another by the sequences of amino acids in their primary
structure, the interaction of the polypeptide chain in the secondary structure and the
folding of these chains in the tertiary structure. Some proteins further have a quaternary structure defined by the combination of different folded polypeptide structures
by hydrogen bonds. One such protein with a quaternary structure is hemoglobin.
Some researchers have explored how to develop other monodisperse polyamides
from proteins as a route to achieving monodispersity in polymerization reactions
(Yang et al. 2003).
Some proteins from aquatic organisms share the same general chemistry as proteins from terrestrial organisms. Proteins such as collagen, luciferase and amylase
are examples of proteins found in land as well as aquatic organisms. However, some
of these proteins have some distinct features in terms of their chemical structure that
differs from one another. The rest of this section will highlight some of the features
specific to aquatic proteins.
Despite some of the adverse effects associated with the consumption of high
quantity of meat, animal protein has the highest amount of all essential amino acids
required for healthy nutrition for humans. To counter the risks associated with meat
consumption such as high fat content leading to cardiovascular disease, it is recommended to consume a diet consisting of mainly plant-based proteins and achieve
the required essential amino acids through a combination of a range of plant protein
sources such as legumes, grains, fruits and vegetables (FAO, WHO 1991).
Despite being considered as highly nutritious consisting of proteins, vitamins and
minerals, amino acid composition of algae is rather limited. Some of the essential
proteins, which are not synthesized by humans and required by the body, are not
present in algae. This is the general case with plant protein, whereby some essential
amino acids are missing in plants of both terrestrial and aquatic. These essential
amino acids missing in plants include leucine, histidine, tryptophan, lysine, valine,
threonine, methionine and phenylalanine (Young and Pellett 1994). The amino acid
missing in particular plant or algae varies from species to species. For example, in
red algae, leucine and isoleucine are usually present in low amounts in brown algae
cysteine, while lysine and methionine are the missing or limited amino acids in brown
algae. Tryptophan and lysine are generally in limited amounts in all algae (Bleakley
and Hayes 2017). Amino acids which are more abundant in algae include aspartic
acid and glutamic acid which could be up to 22–44% in species Fucus sp. and up to
32% in Ulva sp. (Fleurence 1999).
While algae and aquatic plants cannot serve as a main source of proteins due
to the absence of some essential amino acids, they nonetheless can serve as an
additional more efficient protein source. Polypeptides from plant sources tend to be
cyclic peptides, and these are known to have more bioactive properties than the linear
structures. The cyclic structures tend to be more stable than the linear structures (Tan
and Zhou 2006). This stability could ensure they retain their secondary structure