Plasma proteins
Vladimíra Kvasnicová
Plasma proteins
• include proteins of blood plasma and
proteins of interstitial fluid
Distribution in body fluids
• continual movement from blood vesels to
intersticium
• transport by pinocytosis and through
interendothelial junctions
• capillary basal membrane
 molecular sieve
molecule size dependent passage through
protein
Mr
intravascular
(x 103)
albumin
66
(%)
42
transferrin
80
32
haptoglobin 1-1
85
50
IgG
144
44
IgA
160
41
haptoglobin 2-2
160
75
2-macroglobulin
720
92
IgM
971
77
(accepted from book: Clinical Laboratory Diagnostics / Lothar Thomas)
Proteins of interstitial fluid
• subcutaneous: albumin
• lymph: less proteins than in plasma
• liquor: 200x less than in plasma
• patological fluids:
 transsudate
 exsudate
< 30 g/l
> 30 g/l
Plasma proteins
• include proteins of blood plasma and
proteins of interstitial fluid
• almost all are glycoproteins
• some groups of proteins are classified
separatelly (enzymes, proteohormones)
• „total protein“ ~ more than 300 proteins
Individual proteins of blood plasma
The figure is from http://www.beckmancoulter.com/products/instrument/protein/proteomelab_igy_dcr.asp (Feb 2007)
• proteins are ampholytes:
-COOH
-COO- + H+
-NH2 + H+
-NH3+
they are negatively charged
under physiological pH
ANIONS
Common functions of plasma
proteins
• buffer properties (maintenance of pH)
• maintenance of oncotic pressure of blood
• some transport proteins have an
antioxidant function
Classification of plasma proteins
• by
electrophoretic
mobility
 prealbumins
 albumin
 alpha, beta and
gama-globulins
 fibrinogen
The figure is from textbook: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
The figure is from textbook: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley-Liss, Inc.,
New York, 1997. ISBN 0-471-15451-2
Principal proteins of each fraction
immunoglobulins:
IgG, IgA, IgM
2-macroglobulin
haptoglobin
1-antitrypsin
transferrin
orosomucoid
C3-complement
Position of
lipoproteins
in
electrophoretic
patern
The figure is from: Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed. Wiley-Liss,
Inc., New York, 1997. ISBN 0-471-15451-2
• by specific function
 transport proteins
 proteins of immune system
 system of proteases and antiproteases
 proteins of hemocoagulation system
 signal proteins
 enzymes
 cellular proteins
• by clinical use
 cardiomarkers
 tumormarkers
 acute phase reactants
 cellular enzymes
 hormones
 cytokines
Factors influencing concentration
of proteins
total protein: 64 – 83 g/l
• velocity of synthesis and degradation
• distribution in body fluids
• loss into the third place
• elimination from the body
• hydration of the body
other important factors:
• elevation of concentration before taking
blood sample
 body position ( in supine position)
 tightening of arm
• storage of biological speciment
Consequences of abnormal
concentrations
• change in sedimentation of erytrocytes
• swelling
• polyuria
• increased sensitivity to infections
Physiological variability
• increased concentrations




plasma > serum (fibrinogen)
stand-up position (by 10-15 %)
increased muscle activity (by 12 %)
dehydration
• decreased concentrations
 children, pregnant women
 after starvation (albumin, transferrin, C3)
Location of synthesis
• liver
most of plasma proteins
• plasmocytes
• other cells
immunoglobulins
e.g. 2-microglobulin
25 g are synthesized and produced daily
Regulation of synthesis
INCREASE







inflammation
hypertyroidism
hypercotizolism
grows hormone 
irron deficiency
protein loss
clonal production
of Ig
DECREASE
 liver damage with
 parench. tissue
 nutritional deficit
 hypotyroidism
 diabetes mellitus
 alcoholism
Regulation of synthesis
INCREASE







inflammation
hypertyroidism
hypercotizolism
grows hormone 
irron deficiency
protein loss
clonal production
of Ig
DECREASE
 liver damage with
 parench. tissue
 nutritional deficit
 hypotyroidism
 diabetes mellitus
 alcoholism
Catabolism of proteins
location
 liver
 kidneys
 endotelial cells
 other cells
course
 desialization of
glycoproteins
 pinocytosis
 hydrolysis in lysosomes
 use of amino acids
Catabolism of proteins
location
 liver
 kidneys
 endotelial cells
 other cells
course
 desialization of
glycoproteins
 pinocytosis
 hydrolysis in lysosomes
 use of amino acids
• catabolism can be influenced by
 increased sialization of glycoproteins
 target receptors defect
DECREASE IN CATABOLISM OF PROTEINS
• velocity of the catabolism is described by
BIOLOGICAL HALF-LIFE
HALF-LIFE of plasma proteins
• is related to function of a protein
 the longest: structural proteins
 the smallest: regulatory proteins
• it is influenced by
 distribution
 velocity of catabolism and elimination
USE IN DIAGNOSTICS
Elimination from organism
• filtration in the kidneys
excretion with urine
 physilogical loss: < 150 mg/day
• diffusion into gastrointestinal tract
hydrolysis or excretion with feaces
• loss with skin
KNOWLEDGE
of
protein
properties
laboratory
determination
metabolism
and function
distribution
and half-life
use
in diagnostics
correct
interpretation
http://www.sebia-usa.com/products/reagents.html (Feb 2007)