SERUM PROTEIN FRACTIONS & MISCELLANEOUS PROTEINS OF MEDICAL IMPORTANCE (copy)

Prealbumin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Functions

• Indicator of malnutrition

• Binds/transports thyroxine (T4) as TBPA / Transthyretin

Other Comments

• Forms a complex with RBP

• Produces a distinct band in CSF electrophoresis

Albumin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Functions

• Major contributor to plasma oncotic / osmotic pressure

• General transport protein for bilirubin, ions, hormones, free fatty acids, drugs

• Negative APR

Other Comments

• ↓ level in nephrotic syndrome, protein losing enteropathy, malnutrition

• Analbuminemia - absence of albumin

• Bisalbuminemia - two albumin bands

α-Fetoprotein (Serum Protein)

Synthesized in Liver (Hepatocytes)

Alpha 1 globulins

Functions

• ↑ level in amniotic fluid - neural tube defects

Other Comments

• ↑ level in adult serum - hepatocellular carcinoma

α₁-Antitrypsin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Alpha 1 globulins

Functions

• Acute Phase Reactant

• Protease Inhibitor

• Major component of the α₁ region

Other Comments

• Deficiency is associated with SERPINA1 gene mutation and causes juvenile hepatic cirrhosis and pulmonary emphysema

α₁-Acid glycoprotein (Serum Protein)

Synthesized in Liver (Hepatocytes)

Alpha 1 globulins

Functions

• Acute Phase Reactant

• Binds progesterone and some drugs

Other Comments

• Negatively charged even in acid pH; has a very high carbohydrate content

α₁-Antichymotrypsin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Alpha 1 globulins

Functions

• Protease Inhibitor

Other Comments

• Binds prostate-specific antigen

Gc-globulin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Alpha 1 globulins

Functions

• Transports vitamin D > 20,000

Other Comments

• ↓ level may lead to abnormal calcium levels

α₂-Macroglobulin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Alpha 2 globulins

Functions

• Protease inhibitor

• Largest non-Ig protein

Other Comments

• ↑ ten-fold in Nephrotic syndrome & protein losing enteropathy

Haptoglobin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Alpha 2 globulins

Functions

• Acute Phase Reactant

• Binds hemoglobin to preserve iron

Other Comments

• ↓ level seen in hemolytic disorders / intravascular hemolysis

Ceruloplasmin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Alpha 2 globulins

Functions

• Acute Phase Reactant

• Copper-binding protein

• Has oxidase activity

Other Comments

• ↓ level seen in Wilson’s disease

Transferrin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Functions

• Transports iron

Other Comments

• ↑ level seen in IDA (severe) - pseudo paraprotein

• May be estimated using TIBC

C3 complement (Serum Protein)

Synthesized in Liver (Hepatocytes)

Functions

• Immune response

Other Comments

• Most abundant complement component

Hemopexin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Functions

• Binds heme

Other Comments

• ↓ level seen in intravascular hemolysis

β₂-Microglobulin (Serum Protein)

Synthesized in Liver (Hepatocytes)

Functions

• Component of MHC or HLA molecules

Other Comments

• Used to measure GFR

C-reactive protein (Serum Protein)

Synthesized in Liver (Hepatocytes)

Functions

• (+) APR

• Enhances phagocytosis in inflammatory disease

Other Comments

• ↑ up to 1000 times in inflammatory states; hsCRP used as marker for CV risk

Immunoglobulins (Serum Protein)

Synthesized in Plasma Cells

Functions

• Antibodies produced by plasma cells

Other Comments

• Include IgG, IgM, IgA, IgE, and IgD

Myoglobin (Misc. Protein)

Clinical Utility

• Negative predator of Acute myocardial infection

Other Comments

• O2-carrying protein in skeletal and cardiac muscles; detected sooner than troponin but not cardiac specific

Cardiac Troponins (Misc. Proteins)

Clinical Utility

• Gold standard for ACS

Other Comments

• Cardiac-specific and show sustained elevation; TnI with greater cardiac specificity than TnT

Natriuretic Proteins (Misc. Proteins)

Clinical Utility

• BNP and NT-proBNP used as markers for congestive heart failure

Other Comments

• Structurally related neurohormones that affect body fluid homeostasis and blood pressure

Cystatin C (Misc. Proteins)

Clinical Utility

• Endogenous marker for GRF

Other Comments

• Useful when creatinine measurement is not appropriate

β Trace Protein (Misc. Protein)

Clinical Utility

• Endogenous marker for GRF

Other Comments

• Correlates with serum cystatin C and urine microproteins; not influenced by glucocorticoid therapy

Procalcitonin (Misc. Protein)

Clinical Utility

• Biomarker of bacteremia and sepsis

Other Comments

• Increases early in infection (3-6 hours) and has a greater specificity for infection than CRP.

Fibronectin (Misc. Protein)

Clinical Utility

• Plasma FN - marker of Nutritional status (malnutrition)

Other Comments

• Demonstrates a wide variety of cellular interactions, e.g. cell adhesion, differentiation, growth, and wound healing

Cross-linked C Telopeptides (Misc. Protein)

Clinical Utility

• Biochemical marker of bone resorption or osteoporosis

Other Comments

• Proteolytic fragments of collagen I