Proteins are macro-molecules crucial for cell life, which are made up of amino acids (AAs). In healthy people, protein synthesis and degradation are well balanced. However, in the presence of hypercatabolic stimulation (i.e., inflammation), protein breakdown increases as the resulting AAs are consumed for metabolic proposes. Indeed, AAs are biochemical totipotent molecules which, when deaminated, can be transformed into energy, lipids, carbohydrates, and/or biochemical intermediates of fundamental cycles, such as the Krebs’ cycle. The biochemical consequence of hyper-catabolism is protein disarrangement, clinically evident with signs such as sarcopenia, hypalbuminemia, anaemia, infection, and altered fluid compartmentation, etc. Hypercatabolic protein disarrangement (HPD) is often underestimated by clinicians, despite correlating with increased mortality, hospitalization, and morbidity quite independent of the primary disease. Simple, cheap, repeatable measurements can be used to identify HPD. Therefore, identification and treatment of proteins’ metabolic impairment with appropriate measurements and therapy is a clinical strategy that could improve the prognosis of patients with acute/chronic hypercatabolic inflammatory disease. Here, we describe the metabolism of protein and AAs in hypercatabolic syndrome, illustrating the clinical impact of protein disarrangement. We also illustrate simple, cheap, repeatable, and worldwide available measurements to identify these conditions. Finally, we provide scientific evidence for HPD nutritional treatment.

2. Digestion and absorption of proteins
1- Stomach
Protein digestion begins in the stomach where gastric
HCL denatures proteins making them more accessible
to the action of proteolytic enzymes.
Proteins HCl denatured proteins

3. Gastric juice contains 2 proteolytic enzymes : Renin
and Pepsin
Renin is important in digestion of milk in infants .it
is absent in adults
Pepsin is present in stomach as pepsinogen ,
which is activated to pepsin by HCL .
Pepsin is an endopeptidase that act on denatured
proteins changing them into polypeptides chains.

4. 2- Intestine
- Pancreatic secretion is alkaline and
contains proteolytic enzymes:
Trypsin , chemotrypsin, elastase and
carboxypeptidase
These enzymes degrade proteins and
polypeptides into smaller polypeptides,
tripeptides and dipeptides.

5. - Intestinal juice contains three enzymes
Aminopeptidase , tripeptidase and
dipeptidase
These enzymes complete digestion of proteins
into amino acid
Amino Acids are absorbed through an active process
in the intestinal mucosa that is energy dependant and
need carrier molecule.

6. Catabolism of Amino Acids
Proteins are degraded in the following conditions:
1- During normal turnover of tissues
2- Proteins of diet are degraded into amino acids, which are
used for protein synthesis, and if not needed amino acids are
catabolised.
3-During starvation and diabetes mellitus , body proteins are
catabolised for energy production.

7. Amino Acids either
synthesis of new
proteins
catabolised
The Amino group passes
into “Urea cycle ”.
The carbon skeleton
of the amino acid is
converted to either
glucose or ketone
bodies.

8. Ammonia
Although ammonia enters in structure of amino
acids , its accumulation in abnormal high
concentration has toxic effects.
Therefore, ammonia must be eliminated as
soon as formed.

9. Sources of ammonia :
1- Liver:
Transamination of amino acids followed by
deamination of glutamic acid
Transamination collects amino groups from all amino
acids in glutamic acid which undergo deamination in
the liver mitochondria releasing ammonia NH3.

10. Two transaminases are important in clinical
diagnosis of liver and heart diseases :
SGOT = serum glutamic oxaloacetic transaminase
SGPT = serum glutamic pyruvic transaminase

11. 2- Kidney
releases ammonia from glutamine by glutaminase
enzyme.
3- Intestine
a portion of urea diffuses into intestine and
hydrolyzed to ammonia by the action of bacterial
urease enzyme.

12. The main route of elimination of ammonia
is through Urea Cycle
Urea Cycle
Urea is the main end product of protein catabolism .
•Urea is synthesized in liver , released into blood and
cleared by the kidney in urine.
* Measurement of blood urea is a test of kidney
function
Blood Urea level 20 - 40 mg / dl
Urea level in urine 20 - 40 gm / day

14. Ammonia toxicity
Ammonia is a highly toxic product .
Hyperammoniemia is characterized by
comma .
It occurs in conditions as liver cell failure
due to defect of urea cycle .

15. Comma of Ammonia toxicity is due to :
1-Disturbance of Krebs cycle and ATP
production required for brain function.
2- Elevated levels of ammonia produce an
increased permeability to K+ and Cl- ions that
interfere with electrical activity of the brain.

16. Protein energy malnutrition
There are two disorders of protein energy nutrition
widely spread in developing countries :
1- Kwashiorkor
Occurs after weaning.
Inadequate intake of protein in presence of adequate
intake of carbohydrate .
.

17. Kwashiorkor is characterized by
decreased heart functions , low serum albumin level
Clinical picture include anorexia , diarrhea , edema,
growth failure, loss of hair, liver enlargement and
ascites

18. 2- Marasmus
This results from deficiency of proteins and
carbohydrates as in starvation .
It is characterized by generalized wasting