structure of proteins
definition of Digestion
sources of Proteins --> EXOGENEOUS SOURCES 50-100g/day and ENDOGENEOUS SOURCES 30-100g/day
Proteins DEGRADED BY --> HYDROLASES specifically PEPTIDASES(ENDOPEPTIDASES & EXOPEPTIDASES)
1. Gastric Digestion of Proteins
2. Pancreatic Digestion of Proteins
3. Digestion of Proteins by Small Intestine Enzymes
Absorption of Amino ACids by Na+Dependent, Na+ Independent, Meister Cycle or gama-glutamyl cycle
Cultivation of KODO MILLET . made by Ghanshyam pptx
Digestion and absorption of proteins
1. DIGESTION AND ABSORPTION OF
PROTEINS
BY
DR SHRADDHA BHARATH
PG STUDENT
ESIC-MC & PGIMSR
BANGLORE-10
DEPARTMENT OF BIOCHEMISTRY
2. All proteins polymers of L- a amino acids
Proteins AAs Peptide bonds
Total dry body weight 3/4th proteins
3. Digestion hydrolysis of large & complex organic
molecules of foodstuffs smaller and preferably water-
soluble molecules which can be easily absorbed by the
GIT for utilization by the organism.
Digestion as well as absorption complicated process
in GIT.
4. SOURCES OF PROTEINS
Two sources
Exogenous Endogenous
Range- 30-100g/day
- digestive enzymes
- worn out cells of the
digestive tract.
Dietary source
Range-50-100g/day
Animal source
MILK,EGGS,
MEAT,FISH,LIVER,
Vegetable source
CEREALS, PULSES,
PEAS, BEANS &
NUTS
5. About 5-10g/day Lost through feces.
Dietary Proteins Denatured on cooking Easily
Digested.
Proteins are degraded by a class of enzymes namely
Hydrolases.
Specifically cleaves the peptide bonds Peptidases
7. The enzymes responsible for the digestion of
proteins are produced by the
Proteolytic enzymes Inactive
ZymogensActive form.
Proteins Not digested Mouth Absence
of Proteases in saliva.
Stomach
Pancreas
Small Intestine
8. I. GASTRIC DIGESTION OF PROTEINS
Stomach chemical digestion of proteins
Gastric Juice produced by the stomach contains
HCL and PEPSINOGEN
9.
10. HCL
pH of the stomach is <2.
Acid
Denaturation of proteins, more susceptible to
proteases for digestion.
Killing of certain Micro-organisms.
11. PEPSIN (GREEK :PEPSIS DIGESTION)
Secreted by the chief cells/serous cells of the
stomach as PEPSINOGEN.
Pepsinogen Pepsin
Optimum pH around 2
Pepsin ACID STABLE ENDOPEPTIDASE
HCL
12. Digestion of proteins by PEPSIN
PEPTIDES AMINO ACIDS
Hormones( CCK(Cholecystokinin) & SECRETIN)
(DUODENUM)
PANCREATIC JUICE (Enzymes)
13. II. PANCREATIC DIGESTION OF PROTEINS
The optimum pH for the activity of pancreatic enzymes
pH 8 alkaline bile and pancreatic enzymes.
The secretion of pancreatic juice is stimulated by the
hormones, CCK & SECRETIN in intestine
Pancreatic juice TRYPSIN
contains important CHYMOTRYPSIN
endopeptidases namely ELASTASE
CARBOXYPEPTIDASE
14. TRYPSIN ,CHYMOTRYPSIN, ELASTASE, CARBOXYPEPTIDASE
These enzymes are also secreted as Zymogens
(Trypsinogen, Chymotrypsinogen, Proelastase,
Procarboxypeptidase)
These are also c/a SERINE PROTEASES
15. Proteins large polypeptides Small Intestine
Trypsinogen Trypsin hydrolysis of Peptide bond
Enteropeptidase/
Enterokinase
Ca2+
16. 3 Reasons for Big deal of Trypsinogen:
1) Automatically stimulates the conversion of more trypsinogen to
more trypsin during the digestion
2) Chymotrypsinogen Chymotrypsin(active form)
(inactive form)
hydrolysis of internal peptide bond
3) Procarboxypeptidase Carboxypeptidase(active)
(A & B)
hydrolysis of peptide bond from the
carboxyl end
17. CLINICAL CONDITION:
Acute Pancreatitis:
premature activation of trypsinogen autodigestion
Clinical features: mild to severe epigastric pain, with radiation
to the flank, the back or both. Presents with nausea and
vomiting also.
Diagnosis: Blood tests :- Serum Amylase, Serum Lipase,
Serum trypsin / elastase, Hepatic transaminase levels.
Radiological :- ultrasonograpy, CT
18. CHYMOTRYPSIN:
secreted as inactive form zymogen
Chymotrypsinogen
p- chymotrypsin
d-chymotrypsin
a-chymotrypsin
Proteins, peptones smaller peptides & AA
& peptides
TRYPSIN
TRYPSIN
19. CARBOXYPEPTIDASES
The pancreatic Carboxypeptidase (A&B) requires
Zn2+
catalytic activity
Zinc-proteases
Trypsin & chymotrypsin small peptides
Di-peptides tri-peptides AA
CARBOXYPEPTIDASES
20. Exopeptidase
Terminal peptide bond
end Aromatic AA
Eg: Tyrosine,
Phenylalanine or
Tryptophan
Liberates end AA as
“FREE” form
Exopeptidase
Terminal peptide bond
basic AA
Eg: Arginine, Lysine
bearing free –COOH
group
CARBOXYPEPTIDASE-A CARBOXYPEPTIDASE-B
21. III. DIGESTION OF PROTEINS BY SMALL INTESTINE
ENZYMES
Proteolytic enzymes Amino peptidases
present in the di & tripeptidases
intestinal juice
On top of the intestinal cells
presence of Special enzymes c/a BRUSH BORDER ENZYMES
Specifically hydrolyse peptide bonds
22.
23. ABSORPTION OF AMINO ACIDS
Site of absorption
Amino acids absorbed di & tripeptides
ileum & distal jejunum duodenum & proximal
jejunum
Energy requiring process
Transport systems carrier mediated & ATP Sodium
dependent symport system
The free Amino acids, dipepties & some extent of
tripeptides intestinal epithelial cells.
24. THE SMALL INTESTINE POSSESSES AN EFFICIENT SYSTEM TO
ABSORB FREE AMINO ACIDS
L-AMINO ACIDS
More rapidly absorbed
Active process
D- AMINO ACIDS
Simple diffusion
26. AMINO ACID absorption has different mechanism:
1. It is basically a Na+ - dependent active process
linked with the transport of Na+
Energy is supplied indirectly by ATP
27. 2. Na+ - Independent system of amino acid
3. g- GLUTAMYL CYCLE or MEISTER CYCLE
Tripeptide Glutathione( g-glutamyl-cysteinely-glycine)
3 ATP are utilised single amino acid
30. CLINICAL DISORDERS
1. The deficiency of the enzyme 5-oxoprolinase
OXOPROLINURIA (Pyroglutamic Aciduria)
2. The allergy to certain foods(peanuts, sea foods)due to
partially digested proteins
3. Partial gastrectomy
Pancreatitis
Ca. of pancreas
Cystic fibrosis
4. Protein losing Enteropathy
Affects the digestion &
absorption of proteins
31. 5. Transport systems Inborn errors of metabolism such as:
a. Hartnup’s disease
b. Iminoglycinuria
c. Cystinuria
d. Lysinuric protein intolerance
e. Oasthouse syndrome
32. HARTNUP’S DISEASE
Inheritated autosomal recessive disease.
Absorption of neutral amino acids in intestine & reabsorption in renal
tubules defective neutral AA are excreted in urine
Pellagra like symptoms: DERMATITIS & CEREBELLAR ATAXIA
33. LYSINURIC PROTEIN INTOLERANCE
Hyperdibasic aminoaciduria, cationic
aminoaciduria, familial protein
intolerance
An autosomal recessive metabolic
disorder affecting the AA transport
Lysine poorly absorbed in intestine
urinary excretion of this AA is increases
34. OASTHOUSE SYNDROME
Oasthouse (building
designed for drying hops)
Methionine malabsorption
syndrome
An autosomal recessive condition
Symptoms includes :
mental retardation, diarrhea,
convulsions after methionine loading,
oasthouse odour
35.
36. QUESTIONS:
1. Brief about digestion and absorption of proteins ?
2. Give examples of proteolytic enzymes and its specificity
3. Role of hydrochloric acid in protein digestion
4. Name two Endopeptidases with their specifications
5. How is pepsinogen activated. What is the function of
pepsin?
37. Activation of Procarboxypeptidase-A
3 subunits III, II & I
Subunit III subunit II is changed to
inactive proteinase
subunit I active
carboxypeptidase A
TRYPSIN
38. o HARTNUP DISEASE
o Diagnosis Aminoaciduria
increased excretion of indole
compound Obermeyer test
o High protein diet
Supplemetation of Niacin
Minimum exposure to sunlight
o Neuropsychiatric Saditic and
bizarre behaviour of emperors like
Nero & caligula
39. LYSINURIC PROTEIN INTOLERANCE
Hyperdibasic aminoaciduria, cationic
aminoaciduria, familial protein
intolerance
An autosomal recessive metabolic
disorder affecting the AA transport
Lysine poorly absorbed in intestine
urinary excretion of this AA is increased
C/F: skeletal & iminological
abnormalities
Diagnosis : biochemical findings
40. OASTHOUSE SYNDROME
Oasthouse (building
designed for drying hops)
Methionine malabsorption
syndrome
An autosomal recessive condition
Symptoms includes :
mental retardation, diarrhea,
convulsions after methionine loading,
oasthouse odour