Enzymes and Their Vital Role in Human Biology

Among the many proteins in living organisms, enzymes stand out as the most varied and highly specialized. The word enzyme comes from the Greek root enzymos, meaning “to cause change,” which perfectly describes their role in life processes. Every second, hundreds of chemical reactions occur within the human body—processes that would be far too slow to sustain life without the action of enzymes.

An enzyme is a biological catalyst, a type of protein that speeds up chemical reactions without being consumed or permanently altered in the process. Like all catalysts, enzymes do not change the overall balance of a chemical reaction or make impossible reactions occur. Instead, they accelerate reactions that would naturally happen but at a much slower rate—sometimes by factors of millions. They achieve this by lowering the activation energy, the amount of energy required for a reaction to begin. In doing so, enzymes make essential biochemical reactions—such as digestion, respiration, and DNA replication—occur rapidly and efficiently.

Enzymes work by stabilizing the transition state of a reaction, lowering the energy barrier between reactants and products. Each enzyme is specific to a particular reaction or type of molecule, a property known as enzyme specificity. This specificity is determined by the enzyme’s structure. Like all proteins, enzymes are composed of long chains of amino acids folded into precise three-dimensional shapes. The arrangement of these amino acids forms an active site where the substrate—the molecule undergoing change—binds. The exact fit between the enzyme and its substrate is often compared to a “lock and key” mechanism.

There are thousands of different enzymes in the human body, each with a unique function. Digestive enzymes, for instance, break down large food molecules such as proteins, carbohydrates, and fats into smaller components that can be absorbed by the body. Blood enzymes play roles in clotting, while others in cells drive energy production and waste removal.

In short, enzymes are essential for life. Without them, the body’s chemical reactions would be too slow to sustain even the simplest biological functions. Through their remarkable precision and efficiency, enzymes make life’s chemistry possible.
Enzymes and Their Vital Role in Human Biology

Digestive enzymes

Digestive enzymes are often used to support healthy digestion and increase nutrient absorption. Naturally occurring digestive enzymes are proteins that human body makes to break down food and aid digestion. Digestion is the process of using the nutrients found in food to give body energy, help it grow and perform vital functions.

Digestive enzymes are secreted (released) by the salivary glands and cells lining the stomach, pancreas, and small intestine. Their primary role is to help break down the large, complex molecules that make up proteins, carbohydrates, and fats, so that they are small enough for the body to extract and absorb the necessary nutrients.

When the body doesn't make enough enzymes, it can't easily break down foods and absorb nutrients. This is called malabsorption. If human body doesn’t make enough lipase, fat can’t be broken down. Then the body can’t absorb fat-soluble vitamins A, D, E, and K. Likewise, if frequent diarrhea happened because of improper digestion, the patient likely lose electrolytes and water-soluble vitamins.

There are many digestive enzymes. The most important digestive enzymes made in the pancreas include:
*Amylase
*Lipase
*Protease

Some other common enzymes are made in the small intestine, including:
*Lactase
*Sucrase

Fruits, vegetables, and other foods have natural digestive enzymes. Eating them can improve digestion process.
Digestive enzymes

 

Chemical and enzymes in small intestine

Small intestine is a long tube, with a small diameter (about 1 inch), extending from pyloric sphincter to the ileocecal valve. Small intestine can be divided into Duodenum, Jejunum, and ileum.

Food moves through it relatively slowly, over a period of hours, allowing time for the actions of digestion and absorption for which this part of the GI tract is designed. The main classes of human digestive enzymes include proteases, lipases and carbohydrases, which respectively break down the macronutrients protein, fats and carbohydrates.

Up to 3L of intestinal juice is secreted daily by cells in the walls of the duodenum, and to a lesser extent the jejunum and ileum.

Pancreatic and intestinal enzymes that finish the digestion of proteins into amino acids. Proteolytic enzymes, including trypsin and chymotrypsin, are secreted by the pancreas. Carboxypeptidase, a pancreatic brush border enzyme, splits one amino acid at a time.

Proteases - break down proteins at optimum pH 7.9-9.7
• Trypsin and chymotrypsin – break down protein polypeptides in dipeptides
• Carboxypolypeptidase – splits peptides into individual amino acids
• Aminopeptidase and dipeptidase free the end amino acid products

Lipids (fats) are degraded into fatty acids and glycerol. Lipases - break down majority of dietary fats at optimum pH 8.0
• Lipase – hydrolyses triglycerides into free fatty acids and 2-monoglyceride, with the present of bile salt.
• Phospholipase – splits the fatty acids of phospholipids
• Esterase – hydrolyses cholesterol esters

All three are serine proteases, but with different cleavage specificities. Their action is complemented by exopeptidases.

Some carbohydrates are degraded into simple sugars, or monosaccharides (e.g., glucose, galactose) and are absorbed by the small intestine. Pancreatic juice supplies a cocktail of enzymes for the digestion of nearly all major nutrients. α-Amylase is secreted in large amounts. This enzyme is different from the salivary α-amylase, which has a slightly different structure (94% amino acid identity) and is encoded by a different gene.

Pancreatic amylase breaks down some carbohydrates (notably starch) into oligosaccharides. Disaccharidases and oligosaccharidases hydrolyze sucrose and lactose, as well as the maltose, maltotriose, and α-limit dextrins that are formed by the action of α-amylase on starch. Other carbohydrates pass undigested into the large intestine, where they are digested by intestinal bacteria.

Carbohydrases - break down carbohydrates at optimum pH 6.7-7.2
• Amylase – breaks down starch, glycogen and other carbohydrates polysaccharides into disaccharides
Chemical and enzymes in small intestine

Minerals are essential constituents for enzymes

Enzymes are well-known as highly effective and efficient catalysts of a wide variety of processes characterized by high selectivity and activity. Additionally, enzymes may reduce the number of reaction steps and quantities of hazardous solvents needed and thus make a process more inexpensive and environmentally friendly. Many mineral elements are essential constituents of enzymes regulate a variety of physiologic processes.

Sulfur is used in building amino acids, proteins, vitamins, enzymes and chlorophyll. It gives flavor to many crops. Magnesium is at the core of chlorophyll and necessary for the function of enzymes, and to produce carbohydrates, sugars and fats.

Calcium activates enzymes, influences water movement, critical for cell communication. Glutathione peroxidase contains selenium that converts hydrogen peroxide to water. Iron also serves as a cofactor to enzymes in oxidation/reduction reactions (i.e., accepts or donates electrons). These reactions are vital to cells’ energy metabolism.

Iron is necessary for Catalase (cytosol), an enzyme (primarily in liver) that converts hydrogen peroxide to water. Manganese involved in enzyme activity for photosynthesis, respiration and nitrogen metabolism.

Zinc is a component in enzymes and a cofactor in plant growth hormones, facilitates carbohydrate metabolism, protein synthesis and stem growth. Zinc is a catalyst for about 100 enzymes.

Many enzymes and the B-vitamins become active only when a phosphate group is attached. Copper acts as a core to enzymes is used in systems that create carbohydrates and proteins.

Copper is a constituent of several enzymes. Copper-dependent enzymes transport iron and load it into hemoglobin, a protein that carries oxygen through the blood. Copper-dependent enzymes release energy from glucose; provide a natural defense against free radicals that damage the body.

Molybdenum used in enzymes that reduce nitrates to ammonia. Without it protein synthesis is blocked and growth ceases.

Several metalloenzymes which include glutathione peroxidase (Se), catalase (Fe), and superoxide dismutase (Cu, Zn, and Mn) are critical in protecting the internal cellular constituents from oxidative damage.

Only when these metals are delivered in the diet in sufficient amounts can the animal body synthesize these antioxidant enzymes. In contrast, deficiency of those elements causes oxidative stress and damage to biological molecules and membranes.
Minerals are essential constituents for enzymes