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

(x 103)

intravascular(%)

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 < 30 g/l exsudate > 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 chargedunder 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

1-antitrypsin

orosomucoid

2-macroglobulin

haptoglobin

transferrin

C3-complement

immunoglobulins: IgG, IgA, IgM

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

Position of lipoproteins

in electrophoretic

patern

• 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 immunoglobulins

• other cellse.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

KNOWLEDGEof

proteinproperties

metabolismand function

distributionand half-life

laboratorydetermination

usein diagnostics

correctinterpretation

http://www.sebia-usa.com/products/reagents.html (Feb 2007)