This document discusses protein catabolism, which is the breakdown of proteins into amino acids and other simple compounds. It describes how proteins are broken down through digestion and by proteases within cells. The amino acids produced can be used to form new proteins, converted into different amino acids, or further broken down through amino acid catabolism pathways like the Krebs cycle to generate energy. Key aspects of protein catabolism include factors that determine the rate like pH and temperature, and how amino acids gained can be used for protein synthesis or completely degraded for energy release.

1. Mewar institute of management
Protein catabolism
Submitted to: Dr. Namrata Malik
Submitted by: Priya yadav
MSc. biotech. II nd sem

2. What are proteins?
• Proteins are large biomolecules, or macromolecules,
consisting of one or more long chains of amino acid
residues .

3. What is catabolism?
• Catabolism is the set of metabolic pathways that
breaks down molecules into smaller units that are
either oxidized to release energy, or used in
other anabolic reactions.[1] Catabolism breaks down
large molecules (such
as polysaccharides, lipids, nucleic acids and proteins)
into smaller units (such as monosaccharides, fatty
acids, nucleotides, and amino acids, respectively)

4. Protein catabolism
• Breakdown of proteins into amino acids and simple
derivative compounds.
• Digestion process(in intestines) .
• Carried out by non-specific endo- and exo-proteases.
• One example is the subclass of proteolytic enzymes
called oligopeptidase.
• The amino acids produced by catabolism may be directly
recycled to form new proteins, converted into different
amino acids, or can undergo amino acid catabolism to be
converted to other compounds via the Krebs cycle.

5. Overall catabolism of proteins

6. Purpose to catabolise
• Convert proteins into a form of energy that can be
used or stored.
• Deaminated (removal of an amino group)protein can
be processed into the Krebs/Citric Acid (TCA) Cycle to
be converted into usable energy for the organisms.
• Other processes to convert amino acids into usable
molecules to enter the TCA cycle
are transamination (transfer of amino
group), decarboxylation (removal of carboxyl group),
and dehydrogenation (removal of hydrogen).

7. Deamination of amino acids

9. Degradation
• Degradation of proteins occurs within the cells.
• This first step is to breaking the protein down into
amino acids by proteolysis.
• Peptide bonds are broken up by the proteasome
(hydrolyze the peptide bonds)+ ATP + proteases
( cleave off of peptide residues to produce single
amino acids.
• Either glycolysis or the TCA cycle, to produce energy .

10. Cont………..
• In certain organisms, such as bacteria, the proteins
must undergo proteolysis before the amino acids can
be re-polymerized into new proteins because the
original proteins cannot pass through the bacterial
plasma membrane.

11. Factors determining overall rate
• protein half-life, pH, and temperature.
One key component in determining the protein half-life
is based on the N-end rule. This states that the
amino acid present at the N-terminus of a protein
helps determine the protein's half-life.[10]
• In low pH and high temperatures, proteolysis can
begin even without an enzyme.

12. Amino acids gained are used as
• They may be used to synthesize again another set of
protein. Amino acids being a small molecule can be
transported easily to the desired location across
membranes and used to synthesize the desired
protein in the desired place.
• Amino acids can be completely broken to give energy
and waste products. This is the anabolism way by
which energy is released from proteins in the
absence of carbohydrates.

13. Amino acid catabolism
• Amino acids are used as energy sources in some of
the cases. In such cases they undergo
disproportionation with enzymes to give NADH or
pyruvate etc. Some of the examples for amino acid
catabolism is given here.
• Transaminase shifts the alkyl group between amino
acid and pyruvate to get the desired amino acids.
• The scheme of the reaction can be given by

14. • Serine dehydratase catalyses the conversion of
serine to pyruvate and ammonium ion.
• Serine →→ Pyruvate + NH4
+
• Some of the amino acids are converted to the
ketoacids with the conversion of NAD to
NADH

15. Conclusion

16. Reference
• www.google.com
• www.freebooks .com
• Fundamentals of biochemistry

17. • Thankyou