This document summarizes the different types of proteins found in muscle tissue. There are three main categories: myofibrillar proteins, sarcoplasmic proteins, and stroma/connective tissue proteins. Myofibrillar proteins make up 60% of muscle proteins and contribute to water holding capacity, emulsification, and tenderness. They include thick filament proteins like myosin and thin filament proteins like actin. Regulatory proteins like tropomyosin and troponin help control muscle contraction. Sarcoplasmic proteins make up 30-35% of muscle proteins and include myoglobin, which stores and transports oxygen. Stroma proteins include collagen, reticulin, and elastin, which provide structure but influence toughness.
2. MUSCLE PROTEINS:
Proteins are the basic material of tissue structure.
They are the most important component of striated skeletal muscle.
Their classification is correlated with the histological structure of
muscle tissue.
3. TYPES OF MUSCLE PROTEINS:
Muscle proteins have been broadly classified into three
categories:
i) Myofibrillar proteins – soluble in dilute salt solution
ii) Sarcoplasmic proteins – soluble in water or very
dilute salt solution.
iii) Stroma or connective Tissue proteins – almost
insoluble
4. MYOFIBRILLAR
PROTEINS:
• These proteins constitute contractile
part of the muscle and make up
about 60% of the total protein in the
skeletal muscle.
• Myofibrilar proteins are of special
interest to the technologists because
they contribute to approximately 95%
of the water holding capacity, 75% of
the emulsifying capacity and to a large
extent the tenderness.
5. CONT...,
• Thick filaments constitute the A-band of
the sarcomere and consist of the protein
myosin.
• There are 100-400 molecule of myosin in
each thick filament.
• Myosin is a long asymmetrical molecule
containing a globular head and two
identical polypeptide chains.
• It has a relatively high charge and shows
a strong affinity for the divalent cations,
Calcium and magnesium.
6. CONT..,
• The thin filament constitute I-band of the sarcomere and extent on
either side of the Z-line beyond I-band also into the A-band
between the thick myosin filaments.
• Actin is the main protein of the thin filament.
7. REGULATORY PROTEINS:
• Relatively small quantities of other
proteins generally referred
as regulatory proteins are
associated with major
myofibrillar proteins.
• Tropomyosin is a fibrous protein
which occurs as a double helix.
• These helical strands are present
in close association with
in filaments, extending through the
grooves of action helix.
8. • Troponin is another important
regulatory protein which is present in
association with thin filament cementing
the long chain of tropomyosin thread
into the grooves of actin at a regular
interval.
• Troponin is composed of three sub-units:
• Troponin T – binds to tropomyosin and
links it to F-actin filaments.
• Troponin C – binds to calcium ions.
• Troponin I – inhibits or prevents the
interaction between actin and Myosin in
relaxed state.
9. SARCOPLASMIC PROTEINS:
• These proteins make up about 30-35%
of the total proteins in the skeletal
muscle. Myoglobin is a conjugated
protein consisting of a prosthetic
hememoiety and a protein moiety
(globin).
• It provides red colour to the muscle
and serves as a carrier of oxygen to the
muscle fibre.
• It is the most important pigment of
meat colour.
• Cytochrome enzyme, flavin etc.
Contribute very little to meat colour
10. STROMA OR CONNECTIVE TISSUE
PROTEINS :
• The connective tissue is composed of
an amorphous ground substance or
matrix in which formed elements
mostly fibres and a few cells are
embedded.
• The ground substance is a viscous
glycoprotein solution. The
extracellular connective fibres are:
• a. Collagen
• b. Reticulin
• c. Elastin
11. Collagen:
• Collagen is the main fibrous protein the muscles
and significantly influence the meat toughness.
• It makes upto 40-60% of the total stroma protein
and 20-25% of the total protein in the body.
• A fine network of collagen fibres is present in
almost all tissues and organs including skeletal
muscles. It is the most common constituent of
tendons.
• White coloured collagen fibres are straight,
inelastic and non-branching. These fibres shrink
or shorten at a temperature of 600 C but higher
temperatures or boiling causes transformation to
water soluble gelatin.
12. RETICULIN:
•Reticulin is composed of small fibres which resemble that of
collagen except for its intimate association with a lipid containing
myristic acid.
13. Elastin:
• Elastin fibres are branched and do not hydrolyse on boiling.
• Elastin contains two unique amino acids—desmosine and
isodesmosine which contribute to its highly insoluble nature.
• The nutritive value of elastin is practically nil due to its resistance
to digestive enzymes.
