Biological Buffers, Acute Phase Proteins, and Enzymes: Understanding Key Physiological Processes
Biological Buffers
Biological buffers are ionic species that attempt to neutralize excess acid or base to maintain the pH in equilibrium. Principal buffers:
- Intracellular: Phosphate; Glucose 6P; ATP.
- Interstitial: CO3H2/CO3H- (bicarbonate buffer), protein, phosphate.
- Blood – Intraerythrocytic: CO3H2/CO3H- (bicarbonate), Hemoglobin / Oxyhemoglobin; phosphate.
- Plasma: Proteins, Phosphates; CO3H2/CO3H-.
Bicarbonate buffer: CO2 (g) <–> CO2 (dis) <–> CO2 (blood) + H2O <- + zn ++ -> carbonic anhydrase CO3H2 <-> CO3H- + H+ <–> CO3H2 <- Anhydrase carbonic -> CO2 (dis) + H2O <–> CO2 (gas) -> Elimination of breath.
With acidosis, there are too many protons, which leads to more carbonic acid and reduces the production of bicarbonate (CO3H-). It decreases elimination and increases CO3H resorption, and increases the frequency, which lies in its importance in respiratory and renal connection.
Acute Phase Proteins
Acute phase proteins are synthesized in the liver as a response to inflammatory action caused by infection, trauma, etc. This response is called the acute phase response, and the proteins are called acute phase proteins.
Acute phase reactants with positive afterlife:
- Increased plasmatic concentration.
- Increased biosynthesis or secretion.
- Unchanged metabolism.
- Examples: C-reactive protein, alpha-1-antitrypsin, fibrinogen, ferritin.
Acute phase reactants with negative afterlife:
- Decreased plasmatic concentration.
- Increased catabolism.
- Normal biosynthesis may be decreased.
- Examples: albumin, transferrin, alpha and beta lipoproteins.
Acute phase reactants with modified levels:
- Their plasmatic concentration is within normal levels.
- Their biosynthesis and catabolism are compensated.
- Examples: Hemopexin; Kininogen; alpha2 macroglobulin.
C-Reactive Protein (CRP)
C-reactive protein (CRP) is the main acute phase protein. It is synthesized in the liver and is a glycosylated protein with five polypeptide chains. It binds to polysaccharides of bacteria, fungi, nucleic acids, etc. It activates the complement system (C1q). It recognizes toxic substances, binds them, and releases them from circulation. It can increase to 100 or 200 times its normal concentration in the blood during any inflammatory process. It is useful for detecting organic processes, kidney implant rejection, and establishing the activity of inflammatory processes in Rheumatoid Arthritis.
Ferritin
Ferritin is a protein that has the capacity to store iron (0-30%) inside. Serum ferritin is a good indicator of iron reserves in the body.
Increased in:
- Inflammatory processes.
- Aplastic anemia.
- Sideroblastic and hemolytic diseases.
- Hemochromatosis.
- Patients who have received multiple transfusions.
- It is a nonspecific marker in some malignancies.
Decreased in:
- Iron deficiency anemia.
- Iron deficiency states.
Enzymes and Isoenzymes
Enzymes are biological catalysts that accelerate the reaction rate without modifying the equilibrium of 99.9% of the reaction. Enzymes are formed by proteins. They are macroproteins with an active center where the chemical reaction occurs. First, the substrate is recognized, fixed, activated, the reaction occurs, and the product is released.
Isozymes differ in the amino acid sequence, catalyzing the same chemical reaction. These enzymes usually show different kinetic parameters or different regulation. Thanks to them, metabolism adapts to the specific needs of a particular tissue or developmental stage. In many cases, they are codified by homologous genes that have diverged over time.
Creatine Kinase (CK)
In muscle, this enzyme catalyzes the formation of phosphocreatine to store ATP. In muscle activity, the enzyme catalyzes the reverse reaction: Creatine + ATP <-CK-> Phosphocreatine + ADP.
CK is a dimer with two subunits, M and B. There are three isoenzymes:
- CK-1 (BB)
- CK-2 (MB)
- CK-3 (MM)
The BB isoenzyme is in the brain, MM is in skeletal muscle, and the heart contains both MM and MB. CK-MB is of interest in the diagnosis of myocardial infarction, where an increase in total CK and CK-MB indicates a myocardial infarction. It is also relevant in surgery, muscular dystrophies, and exercise.
Diagnosis of Myocardial Infarction
In diagnosing myocardial infarction, the most used marker is Troponin.