Enzymes: Panacea for biochemical reactions and human existence

Enzymes are protein molecules produced within a cell that catalyse all the biochemical reactions in living organisms. The specific sequence of enzymes is encoded by the DNA sequences of corresponding genes. Enzymes are the key molecules that promote growth, being intricately involved in digestion, cell regeneration, cell protection, detoxification, energy supply, and any other biochemical process critical for sustaining life. In the absence of enzymes most of the biochemical reactions either occur very slowly or not at all. Deficiency of an enzyme in the body can trigger body system malfunction affecting various physiological functions.

Enzymes speed up the rate of chemical reactions without being consumed. The human body produces around 1300 enzymes. Some of the examples of enzyme activity include:

·         Digestion, metabolism, and respiration

·         Catabolism of food particles to produce energy

·         Anabolism for the synthesis of essential components

·         DNA replication

·         Nutrient absorption and transportation

·         Detoxification

·         Enhancing immunity

·         Hormone production

·         Cellular repair

·         Signal transduction etc.

Enzymes are substrate-specific and ensure that complex biochemical reactions occur at body temperature (37^o C). There are about 75,000 enzymes detected in the human body. Enzymes are classified into different categories based on the functions they perform e.g., carboxylases, dehydrogenases, hydrolases, isomerases, lipoxygenases, oxidoreductases, kinases, lyases, transferases, etc.

Enzymes are the workhorses of the body and are involved in myriads of biochemical reactions simultaneously. Without enzymes, it is nigh impossible to conduct such reactions with speed, accuracy, and outcomes so vital for the existence of life.

Lack or inhibition of body enzymes can result in the accumulation of unwanted or toxic compounds in the body and affect normal organ functions causing disorders and leading to health problems.  The types of inhibitors include competitive inhibitors that resemble the part of the substrate and hinder access of enzymes to the substrate and non-competitive inhibitors that can change the shape of the substrate impeding substrate reaction. Other factors include the lack of available water - which is an active medium for enzymes to function properly, and higher body temperature - which can deactivate the enzyme, and substrate and enzyme concentrations in the cells.

Some of the metabolic disorders caused by the lack of enzymes because of genetic mutations or genetic alteration include:

·         Lactose intolerance: Inability to digest milk because of lack of enzyme lactase leading to stomach pain, diarrhea, gas, nausea, bloating etc.

·         Galactosemia – Inability to digest breast or cow’s milk because of the absence of enzyme galactose-1-phosphate uridyltransferase (GALT) causing jaundice, vomiting, and liver enlargement.

·         Fabry disease – Lack of enzyme called alpha-galactosidase A leading to accumulation of sphingolipids affecting heart, kidneys, brain, and central nervous system.

·         Maple Syrup urine disease – deficiency of the enzyme branched-chain alpha-keto acid dehydrogenase (BCKD) enzyme causing inability to break down amino acids isoleucine, leucine, and valine.

·         Phenylketonuria (PKU) – Deficiency of enzyme phenylalanine hydroxylase enzyme resulting in increased levels of phenylalanine in the blood leading to intellectual disability.

Enzyme replacement therapy has been introduced to manage the metabolic function caused by the deficiency of certain enzymes. However, there are many other metabolic disorders caused by enzyme deficiency for which the treatment is still not available. For such disorders such as the deficiency of glucose-6-phosphate dehydrogenase causing haemolysis,  the only alternative available is to restrict the intake of foods and drugs that trigger the onset of the disease.

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