ABSTRACT
H u m a n plasm a contain s ove r 20 0 individua l proteins. Som e o f thes e hav e bee n
discussed above , an d Tabl e 7.5 summarize s th e propertie s o f th e majo r p lasm a
proteins. Th e most convenien t w a y o f looking a t plasma proteins i s by employin g
the variou s types o f electrophoresi s (Chapte r 4). The moving-boundary syste m i s
s h o w n i n Figur e 4.12 , w h i ch indicate s tha t seru m ma y b e separate d int o fiv e protein components . O n l y one , albumin , i s a pur e protein . T h e other s ar e mix -
tures o f proteins . Electrophoreti c mobilities o f variou s plasm a protein s ar e als o
indicated i n Tabl e 7.5 . T h u s , th e y-globuli n componen t consist s o f a variet y o f
immunoglobulins o f the I g G type . Take n together, thes e immunoglobulins consti -
Table 7.5 Propertie s o f Some Plasm a Proteins 3
Concentration i n plasm a Molecular
Electrophoretic mobili ty a t p H
Protein (mg/dL) weight of 8. 6 Function
A l b u m i n 3500-5500 66,000 A l b u m i n Osmotic pressure ; transport
Prealbumin 10-40 61,000 Albumin Binds thyroxine c^-Anti trypsin 210-500 45,000 (^-Globulin Inhibits elastas e Orosomucoid 75-100 42,000 a^-Globulin Binds some steroid s TBG 1-2 58,000 a^-Globulin Binds thyroxine Transcortin 7 52,000 a 1 -Globul in Binds steroid s Haptoglobin
Type 1-1 95-212 90,000 a 2 -Globul in Binds hemoglobin Type 2-2 95-212 360,000 a 2 -Globul in Binds hemoglobin
Ceruloplasmin 20-45 140,000 a 2 -Globulin Binds copper , amine, an d i ro n oxidase
a 2 -Macroglobulin 150-420 820,000 a2 -Globuli n Inhibits t rypsi n an d
plasmin Transferrin 200-400 80,000 /3-Globulin Binds i ro n Hemopexin 70-130 57,000 /3-Globulin Binds fre e hemati n Plasminogen 20-40 87,000 /3-Globulin Activated t o
plasmin, wh ic h lyses fibri n
Prothrombin 150 72,000 /3-Globulin Activated i n thrombin, wh ic h clots fibrinoge n
Complement 1 5 100-200 — /3-Globulin Enters int o immun e reactions
Fibrinogen 200-450 340,000 /3-Globulin Clots t o give f ibr i n Immunoglobul in A 90-450 > 160,00 0 /3-Globulin Immun i ty Immunoglobul in M 60-280 1 0 6 /3-Globulin Immuni ty Immunoglobul in G 800-1800 160,000 y-Globulin Immuni ty
aDoes not include lipoproteins. Their properties are discussed i n Chapter 19. bConsists o f nine components .
