FUNCTION OF TRACE MINERALS IN FISH
Himanshu S. Swaina, S. Ratnamanjari
a College of Fisheries, Mangalore, KVAFSU
b Central Institute of Fisheries Education, Versova,
Minerals are non-organic substances that don't fall into the category
of plant or animal but that come from the soil. Minerals perform
several vital functions which are absolutely essential for the very
existence of the organism. Fish require minerals which are the
constituents of certain tissues (mainly skeletal structures) or
molecules that serve as enzyme co-factors and participate in intra-
and extra- cellular ionic balance as well as regulation of endocrine
functions. It has the ability to absorb some inroganic elements not
only from their diets but also from their external environment in
both fresh water and seawater.
The concentration of minerals in the body of an aquatic organism
depends on the food source, environment, species, stage of
development and physiological status of the animal. Most organisms
accumulate and retain minerals from the environment; however, their
incorporation is highly selective. Seven macro- minerals and
15 trace minerals are known to have a definite physiological
role in most animals.
are essential in relative quantity. So also called as "bulk
minerals". Some are structural but many play a role as
Seven principal elements constitute 60 – 80 % of the body’s
inorganic matter. These are Calcium, Phosphorus, Magnesium, Sodium,
Potassium, Chlorine and Sulphur.
Many elements are required in trace amounts,
usually because they play a catalytic
role in enzymes.
So, microminerals are also called traced minerals. These are:
Iron, Copper, Manganese, Iodine, Zinc, Molybdenum, Cobalt, Fluorine,
Selenium, Chromium etc.
About 70% of iron occurs in erythrocytes of blood as a constituent of
haemoglobin. At least 5% of body iron is present in myoglobin of
muscle. Heme is the most predominant iron-containin g substance. It
is a constituent of several proteins/ enzymes (hemopoteins) –
haemoglobin, myoglobin, cytochromes, xanthine oxidase, catalase,
tryptophan pyrrolase, peroxidase. Certain otherproteins contain
non-heme iron e.g. transferrin, ferritin, hemosidein.
Crustaceans which don’t have haemoglobin have much lower
requirements than fin fish and are more sensitive to excess amount.
Iron mainly exerts its functions through the compounds in which it
is present. Hemoglobin and myoglobin are required for the transport
of O2 and Co2.
Cytochromes and certain non-heme proteins are necessary for electron
transport chain and oxidative phosphorylation.
Peroxidase, the lysosomal enzyme is required for phagocytosis and
killing of bacteria by neutrophils.
Iron is associated with effective immuno-competence of the body.
In crustaceans, copper constitutes the main element of proteins such
as haemocyanin or cyanodin which play a role similar to haemoglobin
in oxygen transport requirement is appear as higher than fish.The
body contains about 100 mg copper distributed in different organs. It
is involved in several important functions.
Copper is an essential constituent of several enzymes. These include
cytochrome oxidase, catalase, tyrosinase, superoxide dismutase
(SOD), monoamine oxidase, ascorbic acid oxidase, ALA synthase,
phenol oxidase and uricase. Due to its presence in a wide variety of
enzymes, copper is involved in many metabolic reactions.
Copper is necessary for the synthesis of haemoglobin (Cu is a
constituent of ALA synthase, needed for heme synthesis).
Lysyl oxidase (a copper containing enzyme) is required for the
conversion of certain lysine residues of collagen and elastin to
allysine which are necessary for cross linking these structural
Ceruloplasmin serves as ferroxidase and is involved in the
conversion of iron from Fe 2+ to Fe 3+ in which form iron
(transferin) is transported in plasma.
Copper is necessary for the synthesis of melanin and phospholipids.
Copper also facilitates the absorption of other trace elements such
Development of skeletal system and nervous system ( myelin) requires
Certain copper containing non-enzymatic proteins have been
identified, although their functions are not clearly known. These
include hepatocuprein ( storage form in liver), cerebrocuprein ( in
brain) and hemocuprein ( in RBC).
Hemocyanin, a copper protein complex in shell fishes (invertebrates)
functions like haemoglonin for oxygen transport.
The liver and kidney are rich in Manganese. Within the cells, Mn is
mainly found in the nuclei in association with nucleic acids.
1. Mn serves as a cofactor for several enzymes.These include
arginase, pyruvate carboxylase, isocitrate dehydrogenase, superoxide
dismutase (mitochondrial) and peptidase.
2. Mn is required for the formation of skeleton, proper
reproduction and normal functioning of nervous system.
3. Mn is necessary for the synthesis of mucopolysaccharides
4. Haemoglobin synthesis involves Mn.
5. Mn is necessary for cholesterol biosynthesis.
Most of the body iodine ( 80% ) is present in the thyroid gland.
Muscle, salivary glands and ovaries also contain some amount of
Zinc is mainly an intracellular element.
Zn is an essential component of several enzymes e.g. carbonic
anhydrase, alcohol dehydrogenase, alkaline phosphatase,
carboxypeptidase, superoxide dismutase (cytosolic).
Zinc may be regarded as an antioxidant since the enzyme wuper oxide
dismutase protects the body against free radical damage.
zinc is necessary to maintain the normal levels of vitamin A in
serum. It promotes the synthesis of retinol binding protein.
It is required for wound healing. It enhances cell growth and
division, besides stabilizing biomembranes.
Gusten, a zinc containing protein of saliva is important for taste
It is essential for proper reproduction.
Molybdenum is a constituent of the enzymes xanthine oxidase, aldehyde
oxidase and sulphite oxidase.
Cobalt is only important as a constituent of Vitamin B12.
administration of cobalt stimulates the production of hormone
erythropoietin which promotes erythropoiesis.
Fluoride is mostly found in bones and teeth. The beneficial effect of
fluoride in trace amounts are overshadowed by its harmful effects
caused by excess consumption
Fluoride prvents the dental caries. It forms a protective layer of
acid resistant fluoroapatite with hydroxyapatite of enamel and
prevents the tooth decay by bacterial acids. Further, fluoride
inhibits the bacterial enzymes and reduces the production of acids.
Fluoride is necessary for the proper development of skeleton
It inhibits the activities of certain enzymes. Sodium fluoride
inhibits enolase (of glycolysis) while fluoroacetate inhibits
aconitase ( of citric acid cycle).
Selenium along with vitamin E prevents the development of hepatic
necrosis and muscular dystrophy.
Se is involved in maintaining structural integrity of biological
Se as selenocysteine is an essential component of the enzyme
glutathione peroxidase. This enzyme protects the cells against the
damage caused by H2O2. It appears from recent
studies that selenocysteine is directly incorporated during protein
biosynthesis. Therefore, selenocysteine is considered as a separate
It prevents lipid peroxidation and protects the cells against the
free radicals including superoxide (O-2 ).
Se protects animals from carcinogenic chemicals.
Se binds with certain heavy metals (Hg,Cd) and protects the body
from their toxic effects.
A selenium containing enzyme 5’- deiodinase converts thyroxine
(T4) to triiodo thyroxin in the thyroid gland.
Thioredoxin reductase involved in purine nucleotide metabolism is
also a selenoprotein
In association with insulin, chromium promotes the utilization of
glucose. Cr is a component of a protein namely Chromodulin which
facilitated the binding of insulin to cell receptor sites.
Cr lowers the total serum cholesterol level.
It is involved in lipoprotein metabolism. It decreases serum low
density lipoproteins (LDL) and increase high density lipoproteins
(HDL) and thus promotes health.
It is believed that Cr participated in the transport of amino acids
into the cells (heart and liver).
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Seafood - Fish - Crustacea
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