Researchers are still seeking to fully understand the structural and functional details of enzymes, yet these complex organic molecules are essential to most biological reactions. Enzymes catalyze, or speed up, chemical reactions. The biological processes that sustain an organism depend on numerous chemical reactions, and enzymes ensure that these reactions occur quickly enough to sustain life. Many enzymes, in turn, are dependent on vitamin-derived substances known as coenzymes.
A certain amount of energy, known as activation energy, is needed to initiate any chemical reaction. The fundamental purpose of enzymes is to facilitate reactions by lowering this activation energy. Enzymes accomplish this by binding to reactant molecules and allowing them to interact in a more energy-efficient manner. Reactant molecules bind to enzymes at an intricately structured location known as an active site, and the molecule involved in this binding process is called the substrate. Coenzymes, some of which are vitamins and some of which are synthesized directly from vitamins, activate enzymes by helping the enzyme to bind to its substrate.
Coenzymes activate enzymes primarily by assisting in the transfer of specific particles or compounds involved in the chemical reaction. For example, some coenzymes facilitate enzymatic reactions by carrying electrons and hydrogen ions from one atom to another, while others are involved in transporting entire atoms or larger molecules. Explained another way, an enzyme might not be a perfect fit for the intended substrate unless the active site is modified by the addition of a coenzyme.
The Vitamins That Enzymes Need
The term "vitamin" refers to 13 organic compounds that are essential to human health. In most cases, vitamins must be supplied through diet because the body cannot synthesize them. Vitamins fall into two general categories: water-soluble and fat-soluble. Water-soluble vitamins are found mainly in watery or starchy foods such as grains and vegetables, while fat-soluble vitamins are found mainly in fatty foods such as butter, seafood and organ meats. Only water-soluble vitamins function as coenzymes.
Vitamin deficiencies can lead to serious health disorders because important biological processes break down when a lack of coenzymes prevents enzymes from catalyzing essential chemical reactions. Two well-known coenzyme vitamins are thiamin and niacin. Thiamin compounds serve as coenzymes for a variety of reactions involving cellular energy production, protein synthesis and brain function. Thiamin deficiency causes a disorder known as beriberi, with symptoms such as irritability, weakness and even heart failure. Niacin is needed for numerous reactions related to energy production and fatty-acid synthesis. Deficiency causes pellagra, which leads to dementia, skin problems, weight loss and eventually death.
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