Biochemical Foundations of Human Vital Activity - Volkov, N. I., & Nesen, E. N. 2000

Biochemical Foundations of Human Vital Activity
Enzymes — Biological Catalysts
General Overview of Enzymes

In The Human Body, almost all Chemical Reactions underlying METABOLISM and vital activity proceed very rapidly at a relative constancy of Temperature, pressure, concentration of reacting substances, and the active reaction of the medium. This is possible only due to the presence of biological catalysts. In all Cells of the body, The Role of biological catalysts is performed by Enzymes, or ferments.

Enzymes are highly specialized Proteins that accelerate chemical reactions in cells, i.e., they act as biological catalysts. They cannot initiate new reactions or alter their direction, but they regulate The rate of reactions occurring within the body. Enzymes are used in very small amounts because they exhibit high catalytic activity, and their molecules remain unchanged in the course of catalysis.

A multitude of chemical reactions take place within cells, each controlled by a specific enzyme. Consequently, cells produce many Different types of enzymes that catalyze the transformation of specific substances. Substances whose transformation is catalyzed by an enzyme are called substrates. An enzyme increases the rate of a chemical reaction by lowering the activation energy required for the transformation of substrates.

Enzymes can be located in the fluid part of The Cell (Cytosol) and in individual cell Organelles (Nucleus, Mitochondria, Ribosomes, Lysosomes, etc.), as well as embedded in cell membranes. The fluid part of the cell houses the enzymes of anaerobic carbohydrate oxidation, FATTY ACID Biosynthesis, and the metabolism of many Amino Acids. The Nucleus primarily contains enzymes for nucleic acid synthesis, whereas mitochondria contain enzymes for aerobic oxidation of CARBOHYDRATES and Fatty acids (the entire set of The Citric Acid Cycle) and the Metabolism of individual amino acids. The mitochondrial membranes harbor Enzymes of the Respiratory Chain and Oxidative Phosphorylation processes, which catalyze reactions producing ATP. Ribosomes concentrate proteins biosynthesis enzymes, and lysosomes contain Enzymes for the hydrolytic breakdown of various substances. Each enzyme catalyzes a specific reaction, which ensures the orderly progression of multi-step metabolic processes.

When characterizing the catalytic action of an enzyme, its activity is determined. The unit of activity is defined as The amount of enzyme that catalyzes The conversion of one micromole (10^-6 mol) of substrate per minute under optimal conditions. According to the International System of Units, enzyme activity is typically expressed in katals, which correspond to the amount of enzyme that converts 1 mol of substrate per second. Each enzyme has its own optimal activity conditions under which the reaction proceeds at maximum velocity. The rate of metabolism—and consequently the functional state of the human body and its ability to adapt to Changes in the external and internal environment—depends on enzyme activity and their quantity within the cell.

The science of enzymes is called enzymology. It is currently developing intensively, as knowledge of the MECHANISMS OF ENZYME action and The regulation of their activity plays a major role in various fields of human activity, especially in medicine. Many Diseases of the Organism are associated with changes in enzyme activity or their synthesis processes. This manifests as a disruption in their function and is termed enzymopathy. Currently, about 1,500 hereditary enzymopathies have been identified. For example, the suppression of the Synthesis of the enzyme galactase in infants, which converts galactose into glucose, causes poisoning by excess galactose and death in the first months of life. Many enzymopathies are accompanied by delayed physical development, Metabolic Disorders, and mental disability. Alterations in enzyme synthesis processes do not always cause disease; they may result in changes in secondary traits of the organism, such as eye or Hair color.

Muscular activity can alter the activity and biosynthesis of many enzymes, leading to an increase or decrease in the rate of nutrient Metabolism and Energy production processes during physical work and the recovery period. Physical performance, recovery rate, and the body's adaptation to physical exertion depend on enzyme activity. The action of many Vitamins and other BIOLOGICALLY ACTIVE SUBSTANCES used in sports practice for body recovery and weight regulation is related to enzymes. By acting on enzymes, it is possible to alter and correct the rate of metabolism.

Currently, three main nomenclatures are used for naming enzymes: trivial, rational, and systematic.

Trivial nomenclature represents a working name of enzymes that does not reflect their specific action. For example, Protein Hydrolysis in the gastrointestinal tract is carried out by Pepsin (from Greek pepsis — Digestion) and Trypsin (from Greek tripsis — to liquefy/soften). A group of colored intracellular enzymes that accelerate oxidation-reduction reactions is called Cytochromes (from Latin citos — cell and chroma — color).

According to rational nomenclature, the name of an enzyme is formed from the name of the catalyzed substance with The addition of the suffix "ase". Thus, the enzyme accelerating starch hydrolysis is called amylase (from Latin amilum — starch), fat breakdown — lipase (from Greek lipos — fat), sucrose breakdown — sucrase, ATP hydrolysis — ATPase, and so on.

The systematic nomenclature of enzymes, recommended by the International System of Units, includes the name of the substrate and the type of catalyzed reaction with the addition of the suffix "ase". If the substrate is in the form of ions, its name uses the suffix "ate". Thus, according to this nomenclature, the enzyme that catalyzes The oxidation of lactic acid (lactate) in body Tissues is called Lactate dehydrogenase. Systematic nomenclature makes it possible to determine what reaction the enzyme catalyzes.

Enzymes are widely used in various spheres of human activity. Since ancient times, they have been employed in cheese making, alcohol production, as well as in baking, brewing, The production of Antibiotics, vitamins, and more. Modern industry produces over 200 enzymatic preparations used in medical practice for the Prevention and Treatment of various diseases. For instance, in gastrointestinal tract disorders, trypsin, Chymotrypsin, lipase, and amylase are used as enzymatic preparations (betacid, obomin, panzinorm, etc.). The enzyme hyaluronidase in the form of lidase and ronidase preparations is used for joint lesions, edema, wounds, and bruises. Lysozyme is used in the treatment of Conjunctivitis, cytochrome c oxidase for oxygen deficiency, collagenase for the resorption of scar tissue, and Elastase for the prevention of atherosclerosis.

In the treatment of various diseases, including those of The Musculoskeletal System and post-traumatic changes, the method of systemic enzyme therapy is used. It is based on the complex action of A number of multi-enzyme preparations (wobenzym, phlogenzym, etc.) on numerous biochemical processes in the body.

Enzymes are also used in Diagnostics of the functional state of the body in medicine and modern sports.