Diagnostic Enzymes: The Serum markers in Clinical Analysis and Biosensors

Enzymes as biocatalysts have been widely used in industrial processes such as food processing, beer fermentation, laundry detergents, pickling purposes, and control, as well as accelerate, the catalytic reactions in order to quickly and precisely obtain various valuable end products.

diagnostic enzymes details

The enzymes are more frequently used in both laboratories and commercially for the purpose of stereospecific bioconversion, utilization of waste into useful end products for a better environment, for the production of raw materials and many more.

What are the Diagnostic enzymes?

The diagnosis of the serum level of certain enzymes has been used as an indicator of cellular damage that results in the release of intracellular components into the bloodstream.

Hence, when a physician reveals that a person has to undergo a neurological enzyme assay, the purpose is to ascertain whether or not there is brain damage.

The diagnosis of certain enzymes serum levels has been used as an indicator of cell damage, resulting in the release of intracellular components into the blood.

Therefore, when doctors show that a person should receive the enzyme nervous system, the goal is to determine if there is an assay of brain damage.

Enzymes are biological catalysts responsible for supporting almost all of the chemical reactions that maintain animal homeostasis.

Because of their role in maintaining life processes, the assay and pharmacological regulation of enzymes have become key elements in clinical diagnosis and therapeutics. 

Liver disease

The liver is the largest internal organ and plays an important role in many functions of the body, including blood detoxification, cholesterol, glucose, iron metabolism, etc.

Various conditions affect the normal functioning of the liver, including hepatitis, Epstein Barr virus infection, fatty liver.

In these anomalies, several enzymes are released into the blood, and quantification of these catalysts can lead to disease detection.

The measurement of the serum levels of numerous enzymes has been shown to be of diagnostic significance as Diagnostic Enzymes.

This is because the presence of these enzymes in the serum indicates that tissue or cellular damage has occurred resulting in the release of intracellular components into the blood.

Commonly assayed enzymes are the aminotransferases:

  • Alanine Transaminase (ALT): sometimes still referred to as Serum Glutamate-Pyruvate aminoTransferase, SGPT) and
  • Aspartate Aminotransferase (AST): It is also referred to as Serum Glutamate-Oxaloacetate aminoTransferase, SGOT);
  • Lactate dehydrogenase (LDH)
  • Creatine Kinase (CK): It is also called creatine phosphokinase, CPK);
  • Gamma-Glutamyl Transpeptidase (GGT)

Other enzymes are assayed under a variety of different clinical situations but they will not be covered here.

Enzyme Disorder / Disease
Acid Phosphatase Malaria
Alanine aminotransferase Hepatocellular damage and Hepatitis B and C
Alkaline phosphatase Chronic kidney disease, Oseomalasis, Type II diabetes, Obstructed Liver
Amylase Pancreatitis and Myocardial infraction
Aspartate aminotransferase Hepatic diseases, Dental disorder, Liver fibrosis
Creatine kinase Myocardial damage, Neuroleptic malignant syndrome
Gamma glutamyl transferase Cardiovascular mortality,
Gelatinase-B Gastric cancer, Vascular dementia, Rheumatoid arthritis, Malignant gliomas
Glucose-6-phosphatase Gierke disease, Hypoglycemia
Lipase Acute pancreatitis, Skin disorders
Lysozyme Rheumatoid arthritis, Tuberculous meningitis, Tuberculous pericarditis
Lactate dehydrogenase Pyroptosis, Necrosis, Breast cancer
Glucose-6-phosphate dehydrogenase  

Gastric cancer

Hence, when a physician indicates that he/she is going to assay for liver enzymes, the purpose is to ascertain the potential for liver cell damage.

AST and ALT:

The typical liver enzymes measured are AST and ALT. ALT is particularly diagnostic of liver involvement as this enzyme is found predominantly in hepatocytes.

When assaying for both ALT and AST the ratio of the level of these two enzymes can also be diagnostic. Normally in liver disease or damage that is not of viral origin, the ratio of ALT/AST is less than 1.

However, with viral hepatitis, the ALT/AST ratio will be greater than 1. Measurement of AST is useful not only for liver involvement but also for heart disease or damage.

The level of AST elevation in the serum is directly proportional to the number of cells involved as well as on the time following an injury that the AST assay was performed. Following injury, levels of AST rise within 8 hours and peak 24–36 hours later.

Within 3–7 days the level of AST should return to pre-injury levels, provided a continuous insult is not present or further injury occurs. Although measurement of AST is not, in and of itself, diagnostic for myocardial infarction, taken together with LDH and CK measurements (see below) the level of AST is useful for timing of the infarct.

Lactate Dehydrogenase (LDH)

The measurement of LDH is especially diagnostic for myocardial infarction because this enzyme exists in five closely related, but slightly different forms (isozymes). The 5 types and their normal distribution and levels in non-disease/injury are listed below.

  • LDH 1 – Found in heart and red blood cells and is 17% – 27% of the normal serum total.
  • LDH 2 – Found in heart and red blood cells and is 27% – 37% of the normal serum total.
  • LDH 3 – Found in a variety of organs and is 18% – 25% of the normal serum total.
  • LDH 4 – Found in a variety of organs and is 3% – 8% of the normal serum total.
  • LDH 5 – Found in the liver and skeletal muscle and is 0% – 5% of the normal serum total.

Following a myocardial infarction, the serum levels of LDH rise within 24-48 hours reaching a peak by 2–3 days and return to normal in 5-10 days. Especially diagnostic is a comparison of the LDH-1/LDH-2 ratio. Normally, this ratio is less than 1.

A reversal of this ratio is referred to as a “flipped LDH”. Following an acute myocardial infarction, the flipped LDH ratio will appear in 12–24 hours and is definitely present by 48 hours in over 80% of patients.

Also important is the fact that persons suffering chest pain due to angina only will not likely have altered LDH levels.

Creatinine Phospho Kinase (CPK)

CPK is found primarily in the heart and skeletal muscle as well as the brain. Therefore, the measurement of serum CPK levels is a good diagnostic for injury to these tissues.

The levels of CPK will rise within 6 hours of injury and peak by around 18 hours. If the injury is not persistent the level of CK returns to normal within 2–3 days.

Like LDH, there are tissue-specific isozymes of CPK and their designations are described below.

  • CPK3 (CPK-MM) is the predominant isozyme in muscle and is 100% of the normal serum total.
  • CPK2 (CPK-MB) accounts for about 35% of the CPK activity in cardiac muscle, but less than 5% in skeletal muscle and is 0% of the normal serum total.
  • CPK1 (CPK-BB) is the characteristic isozyme in the brain and is in significant amounts in smooth muscle and is 0% of the normal serum total.

Since most of the released CPK after a myocardial infarction is CPK-MB, an increased ratio of CPK-MB to total CPK may help in the diagnosis of acute infarction, but an increase of total CPK in itself may not.

CPK-MB levels rise 3–6 hours after a myocardial infarct and peak 12–24 hours later if no further damage occurs and returns to normal 12–48 hours after the infarct.

Some Enzymes and Related Diseases (Diagnostic Enzymes):

  • Acid Phosphatase – Some Prostatic diseases
  • Alanine aminotransferase (ALT) -Liver, Heart diseases
  • Aldolase – Some muscle diseases
  • Alkaline Phosphatase – Liver and Bone diseases
  • Amylase – Pancreatic diseases
  • Angiotensin-Converting Enzyme (ACE) – Active Sarcoidosis
  • Aspartate aminotransferase (AST) – Heart, Liver diseases
  • Cholinesterase (pseudocholinesterase) – Acute organophosphorus poisoning
  • Creatine Kinase (CK or CPK) – Heart, Muscle diseases
  • Gamma-Glutamyltransferase (GGT) – Liver disease, alcohol rehabilitation
  • Lactate Dehydrogenase (LDH)– Heart, Liver, Brain diseases
  • Lipase -Pancreatitis
  • Lysozyme – Some acute leukemias

So, there is more importance of enzymes in clinical diagnosis.

Enzymes as Diagnostic tools

A biosensor is an analytical device that incorporates a biological or biologically derived sensing material with close proximity to the physicochemical transducer. The main purpose of such a device is to generate a discrete or continuous signal that is proportional to the concentration of the analyte.

The first biosensor was developed in 1962 for the detection of glucose, based on immobilized glucose oxidase, using an oxygen electrode as a transducer

Biosensors

This biosensor is configured and assembled with numerous components. The basic principle is to convert a biologically induced recognition event into a usable signal.

Transducer

Examples

Electrochemical

Clark electrode; mediated electrode; ion-selective electrode (ISE); field-effect transistor (FET)-based device
Optical

devices 

Photodiodes; waveguide systems; integrated optical devices
Calorimetric Thermistor; thermopile

Piezoelectric

Quartz crystal microbalance (QCM); surface acoustic wave (SAW) devices

Magnetic Bead-based devices

Enzymes based biosensors in Diagnosis

  1. Biosensors for blood glucose: It is for glucose monitoring have been developed using various types of enzymes. Eg:
    • Glucose dehydrogenase based Glc biosensors,
    • Cellulose dehydrogenase-based Glucose Biosensors,
    • Glucose Oxidase based Glucose biosensors
  2. Biosensors for Urea in Blood and Urine: This biosensor is for urea detection are generally based on urease.
  3. Biosensors for Uric Acid: The biosensor was fabricated by using a carbon paste electrode entrapped uricase, and the tetracyanoquino-dimethane as a redox mediator
  4. Biosensors for Lactic acid: This biosensor works based on the enzyme lactate oxidase, which catalyzes the oxidation of lactic acid, which forms pyruvate and hydrogen peroxide.
  5. Biosensors for Arginine: This biosensor works based on the Arginine levels.
  6. Biosensors for Asparagine: This biosensor is used for the detection of asparagine in the human blood samples for leukemia analysis.

Final words

Enzyme and enzyme-based biosensors are valuable tools for the clinical diagnosis of various disorders due to their high specificity, irritation, rapid response, ease of self-testing, portability, and so forth.

The high specificity of enzymes advocates their choice for medical diagnostics. A research survey reveals lots of reports on the use of enzymes in clinical diagnostics.

Most of the research conducted on enzymes in diagnostics is carried out at the laboratory scale. So, it is most important to commercialize the applications of enzymes used in diagnostics of various diseases.

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