2. INTRODUCTION TO PROTEIN
Protein makes up approximately 20 percent of the human
body and is present in every single cell. The word protein is a
Greek word, meaning of “utmost importance.” Proteins are
called the workhorses of life as they provide the body with
structure and perform a vast array of functions. You can stand,
walk, run, , swim, and more because of your protein-rich
muscles. Protein is necessary for proper immune system
function, digestion, and hair and nail growth, and is involved
in numerous other body functions. In fact, it is estimated that
more than one hundred thousand different proteins exist
within the human body.
3. WHAT IS PROTEIN?
• Proteins, simply but, are macromolecules composed of amino
acids. Amino acids are commonly called protein’s building
blocks. Proteins are crucial for the nourishment, renewal,
and continuance of life. Proteins contain the elements carbon,
4. Properties Of Proteins:
Proteins are the most abundant biological
macromolecules, occurring in all cells. The building
blocks of proteins are the twenty naturally occurring
amino acids. Thus, are the polymers of the amino
acids that are linked together by peptide bonds.
➢ COLOUR AND TASTE: Proteins are colourless and usually taste less. They are
homogenous and crystalline.
➢ SHAPE AND SIZE: The proteins range in shape from simple crystalloid spherical
structure to long fibrillary structure.
➢ MOLECULAR WEIGHT: Different proteins have different amino acid composition and
hence their molecular weights differ. The proteins generally have large molecular weights
ranging between 5 x 103 and 1 x 106 . Values of molecular weight of many proteins lie close
to all multiple of 35000 and 70000.
Physical Properties Of Proteins :
5. ➢ COLLOIDAL NATURE: Because of their giant size, the proteins exhibit many colloidal
properties such as; their diffusion rates are extremely slow and they may produce considerable
light – scattering in solution, thus resulting in visible turbidity (Tyndall effect).
➢ DE-NATURATION AND RE-NATURATION: Proteins are sensitive molecules and can be
s de-natured by some agents such as heat and urea that cause unfolding of polypeptide chains
without causing hydrolysis of peptide bonds. Some naturing agents are small pH, radiations,
heat, urea etc. If a de-natured protein return to its native state after the de-naturing agent is
removed, the process is called re-naturation.
➢ AMPHOTERIC NATURE: Like amino acids, the proteins are also amphoteric that is they
act as acids and alkalis both.
➢ ISOELECTRIC POINT:. The Isi-electric point (pl) is the PH at which the number of positive charges
equals the number of negative charges. And the overall charge on the amino acid is equal. At this point, when
subjected to an electric field the proteins do not move either towards anode or cathode. Hence this property is used
to isolate proteins
➢ IRON BINDING CAPACITY: The proteins can form salts with both cations and anions based on net
charge.
➢ OPTICALACTIVITY: All proteins solutions rotate the plane of polarized light to the left that is these are
lavatory.
6. ➢ HYDROLYSIS: Proteins are hydrolyzed by a variety of hydrolytic agents.
▪ By acidic agents ▪ By alkaline agents
➢ REACTIONS INVOLVING COOH GROUP: Some reactions involving COOH
are
▪ Salt formation ▪ Esterification ▪ Reaction with amines
➢ REACTIONS INVOLVING NH2 GROUP: Some reactions involving NH2 group
are
▪ Salt formation ▪ Reaction with Sanger’s reagent
▪ Reaction with formaldehyde ▪ Van Slyke reaction
▪ Reaction with benzaldehyde ▪ Acylation
➢ REACTIONS INVOLVING R GROUP OR SIDE CHAINS: Some reactions are
▪ Biuret test
▪ Xanthoproteic test
➢ REACTION INVOLVING SH GROUP: Some reactions are
▪ Nitroprusside test
▪ Sullivan test
CHEMICAL PROPERTIES OF PROTEINS
▪ Pauly test
▪ Ehrlich test
▪ Folin’s test
▪ Sakaguchi test
➢ REACTIONS INVOLVING BOTH COOH AND NH2 GROUP: Some reactions are
▪ Ninhydrin reaction
▪ Reaction with phenyl isocyanate
▪ Reaction with Edman reagent
▪ Reaction with phosgene
▪ Reaction with carbon disulphide .
7. CLASSIFICATION OF PROTEINS:
The ability to serve a variety of functions is characteristic of most biomolecules. Nowhere is this
versatility better exemplified than by the proteins. Perhaps because of their many functions,
proteins are the most abundant organic molecules in living cells, constituting more than 50
percent of the mass once water is removed. It is estimated that the human body contains well
over a million different kinds of protein, and even a single-cell organism contains thousands.
Each of these is a polymer of amino acids which has a highly specific composition, a unique
molecular weight (usually in the range from 6000 to 1 000 000) and its own sequence of
different amino acids along the polymer chain.
CLASSIFICATION BASED ON COMPOSITION:
Proteins may be divided into two major classes on the basis of their behavior when reacted
with water. The products obtained upon hydrolysis of simple proteins are all amino acids. In
the case of conjugated proteins other organic and/or inorganic substances are obtained.
The non-amino acid portions of conjugated proteins may consist of metals, lipids, sugars,
phosphate, or other types of molecules. These components are referred to as prosthetic
groups.
8. FIBROUS PROTEINS:Proteins may also be subdivided on the
basis of their molecular shape or conformation. In the fibrous
proteins long polymer chains are arranged parallel or nearly
parallel to one another to give long fibers or sheets. This
arrangement results in physically tough materials which do not
dissolve in water. The fibrous proteins are fundamental
components of structural tissues such as tendons, bone, hair,
horn, leather, claws, and feathers.
GLOBULAR PROTEINS: By contrast, polymer chains of the
globular proteins fold back on themselves to produce compact,
nearly spherical shapes. Most globular proteins are water-
soluble and hence are relatively mobile within a cell. Some
examples are enzymes, antibodies, hormones, toxins, and
substances such as hemoglobin whose function is to transport
simple molecules or even electrons from one place to another.
The enzyme trypsin, is a typical globular protein.
Hemoglobin, a globular,
conjugated protein. Note
the prosthetic group (heme) in
green.
Collagen, a fibrous, simple
protein.
9. MEMBRANE PROTEINS :
Another class of proteins are the membrane
proteins, which, as the name would suggest,
reside in a cell's lipid bilayer membrane. Such
proteins can act as channels for ions or other
molecules unable to pass through the lipid
bilayer; as signal transducers, able to respond to
signal molecules on one side of a membrane to
begin a molecular response on the other side of
the membrane; or as anchors of other molecules
to the cell membrane, to name a few exemplars
of membrane protein function. Because these
proteins interface with non-polar portions of the
lipid bilayer, they do no maintain function and
structure in an aqueous solution, making them
far more difficult to study than globular proteins
or fibrous proteins
1. a single transmembrane. 2. a polytopic
transmembrane α-helical protein 3. a
polytopic transmembrane β-sheet protein
10. Amino acids Metabolism in Mammals
Protein metabolism is the chemical cycle of breaking
down protein (catabolism) and using the components to
synthesizing (anabolism) new molecules to be used in the
body. The process is also known as proteometabolism .
General metabolism of amino acids:
• Anabolic pathway • Catabolic pathway.
General metabolism of amino acids: • Dietary proteins and
body proteins are broken down to amino acids. This is
called catabolic reactions. In transamination reaction,
amino group of amino acid is removed to produce the
carbon skeleton (keto acid). The amino group is excreted
as urea. The carbon skeleton is used for synthesis of non-
essential amino acids.
It is also used for gluconeogenesis or for complete
oxidation. Amino acids are used for synthesis of body
proteins; this is anabolic reaction.
11. • Formation of Ammonia • The first step in the catabolism of
amino acids is to remove the amino group as ammonia. Ammonia is
highly toxic especially to the nervous system. Detoxification of
ammonia is by conversion to urea and excretion through urine.
CATABOLISM OF AMINO ACID
Transamination is the exchange of amino group between amino acid
and another acid, forming a new alpha amino acid. The enzyme
catalysing the reaction is known as transaminases (amino
transferases) keto-group. These enzymes have pyridoxal phosphate
prosthetic group. The reaction is readily reversible.
Biological significance of transamination:
1.First step of catabolism: Ammonia is removed, and rest
of the amino acid is entering into catabolic pathway.
2. Synthesis of non-essential amino acids: By means of
transamination, all non-essential amino acids could be
synthesized by the keto acids available for other sources
body from
A . Transamination:
12. • After the transamination reactions that transfer
amino groups, oxidative deamination occurs by
glutamate dehydrogenase results in the liberation
of the amino group as free ammonia from
Glutamate. This reaction is occurs in the liver.
• The α-keto acids enter the central pathway of
energy metabolism and ammonia in urea
synthesis, liberated after oxidative deamination.
•Glutamate is a unique amino acid that only
undergoes rapid oxidative deamination, that is
catalyzed by glutamate dehydrogenase.
•The glutamate dehydrogenase of mammalian
liver has the unusual capacity to use either NAD+
or NADP+ as cofactor.
B. Deamination
13. C. Urea Cycle
The cycle is known as Krebs-Henseleit cycle as
this pathway was discovered in 1932 by Hans
Krebs and Kurt Henseleit . As ornithine is the
first member of the urea reaction sequences, it is
called as Ornithine cycle. The two nitrogen
atoms of urea are derived from two different
sources, one from ammonia and the other
directly from aspartic acid.
•Urea production occurs almost exclusively in
the liver and ultimately excreted through kidneys
in form of urine
There are fives steps in the Urea Cycle:
1- Formation of carbamoyl phosphate
2-Formation of citrulline
3- Formation of argininosuccinate
4- Formation of arginine and fumarate
5-Formation of urea and ornithine
. Regulation of the urea cycle • During starvation, the
activity of urea cycle enzymes is elevated to meet the
increased rate of protein catabolism. The major regulatory
steps is catalyzed by CPS-I (Carbamoyl phosphate
synthetase-I) • where the glutamate positive (NAG).
effectror is N-acetyl 29
14. Protein metabolism related disorders:
Individuals with MSUD must remain on a
protein-restricted diet that limits the
amount of branched-chain amino acids
they can eat. Protein-restriction must start
as soon as possible after birth to promote
proper growth and development. Diet
management is a constant balancing act
between giving enough food, protein and
BCAAs to provide for normal growth and
development.
MSUD is a recessive genetic disorder. The
four varieties of MSUD are caused by
mutations, or changes, in the genes that are
related to the BCKDC enzymes. When those
genes are defective, the BCKDC enzymes
aren’t produced or don’t work properly.
These gene mutations are inherited
on the chromosomes you receive from your
parents
Lethargy
Poor appetite
Weight loss
Irritability
Irregular sleep patterns
High pitched cry
Maple syrup urine disease is an inherited
disorder in which the body is unable to process
certain protein building blocks (amino acids)
property. Amino acids are what remain after
your body digests protein form the food you
eat. Special enzymes process amino acids so
they can be used to maintain all your body
functions.
1. MAPLE SYRUP URINE DISEASE
15. 2.GAUCHER DISEASE
Type 1: It is the most common form of the disease and is also known as non-neuronopathic as it does not involve the central nervous system.
Type 2: It is known as acute neuronopathic Gaucher disease. It occurs in newborns and infants and is characterized by neurological
complications. The life expectancy of children with type 2 Gaucher disease is very low with death occurring at 1-3 years.
Type 3: It known as chronic neuronopathic Gaucher disease. It occurs during the first decade of life. Patients are able to survive through their
20s and 30s.
.
Enzyme replacement therapy (ERT) is used
for type 1 patients and is effective. ERT is
also used for type 2 and type 3 patients
but it is unable to reverse the neurological
symptoms.
Treatment:
The symptoms of the disease may vary in
patients, some are asymptomatic while some
might face serious complications.
Abnormally enlarged liver or spleen
Anemia
Low levels of platelets which may cause
bleeding problems
Skeletal abnormalities
Symptoms:
Types of Gaucher Disease:
Gaucher disease is a lysosomal storage disorder (LSD) in which deficiency of the enzyme glucocerebrosidase results in
the accumulation of harmful quantities of certain fats (lipids), specifically the glycolipid glucocerebroside , throughout
the body especially within the bone marrow, spleen, and liver. It’s caused by a mutation in the CBA gene.
16. 3.KWASHIORKOR
It is a condition, mostly occurring in children or famine areas, in which there is diet is rich in carbohydrates but it
either contains very less amount or completely lacking proteins. Kwashiorkor can also occur due to parasites and
infections that can interfere with nutritional status. Low protein diets associated with dietary changes due to milk
allergies in infants, fad diets, poor nutritional education, or a chaotic home life, are other causes of
kwashiorkor.
• Fatigue
• Frequent infections
• Generalized swelling
• Hair and nail changes, including brittle, reddish hair and ridged nails
that are thin and soft
• Irritability
• Muscle wasting
• Skin changes, including pigment loss, red or purple patches, peeling,
cracking, skin sloughing, and the development of sores
• Slowed growth leading to short stature
• Weight loss
• Abdominal swelling, distension or bloating
• Diarrhea
• Enlarged liver
Symptoms of kwashiorkor
17. 4. PHENYLKETONURIA
Newborns with PKU initially don't
have any symptoms.
PKU signs and symptoms can be
mild or severe and may include:
• A musty odor in the breath, skin
or urine, caused by too much
phenylalanine in the body
• Fair skin and blue eyes, because
phenylalanine can't transform
into melanin.
• Hyperactivity
• Intellectual disability
• Abnormally small head
SYMPTOMS:
Phenylketonuria is the most common clinically encountered inborn error of amino acids metabolism. Our bodies break down
the protein in foods, such as meat and fish, into amino acids, which are the "building blocks" of protein.
These amino acids are then used to make our own proteins. Any amino acids that are not needed are broken down further and
removed from the body.
It’s characterized by accumulation of phenylalanine and a deficiency of tyrosine.
A defective gene (genetic
mutation) causes PKU,
which can be mild,
moderate or severe. In a
person with PKU, this
defective gene causes a lack
of or deficiency of the
enzyme that's needed to
process phenylalanine, an
amino acid.
.
CAUSES:
