Enzymes (enzymes) are specific proteins that act as biological catalysts; produced by the cells of living organisms.
Enzymes differ from conventional catalysts their greater specificity (see below)and the ability to accelerate chemical reactions under conditions of normal functioning of the body.
Enzymes are present in all living cells, animal, plant, bacteria. Most of the enzymes in the tissue in very small concentrations, but there are cases when the enzymatic activity has a protein that forms a significant part of the cell plasma, such as myosin in muscle tissue. Molecular weight enzymes varies widely: from a few thousand to several million, and similar enzymes, but allocated from various sources, may have different molecular weight, a different sequence of amino acid composition.
Enzymes that have the same catalytic effect, but differing in their physical and chemical properties, are called isoenzymes (isoenzymes). The enzymes can be simple or complex proteins. The latter, in addition to protein (apparment), incorporate and non-protein component of the remainder of organic molecules or inorganic ion. Easily detachable from apparment non-protein component is called coenzyme. Strongly associated with non-protein enzyme part is called the prosthetic group. Many prosthetic group and coenzymes are derived vitamins, pigments and other enzymes have a strict specificity with respect to the substrate (i.e. selectively interacts with certain chemical substances and compounds). For example, lactase (located in the intestinal juice) decomposes only a disaccharide lactose and lactose derivatives (lactobionic acid, Victoriei and others) with the formation of a mixture of glucose and galactose; Maltese splits maltose on two molecules of glucose, and amylase is valid only for starch, glycogen and other polysaccharides.
As a result of consistent actions listed, as well as other enzymes of carbohydrate food converted into monosaccharides and are absorbed by intestinal wall. Specificity of enzymes is that they are interacting with a specific chemical grouping of the substrate. For example, pepsin (see) acts on proteins, communication breaks down inside polypeptide chains of protein molecules, and the protein molecule is split into polypeptides, which are then under the action of other enzymes trypsin (see), chymotrypsin (see) and peptidases can be broken down into amino acids. Specificity of enzymes plays, thus, the biological importance; thanks to her body by means of a sequence of flow of chemical reactions. Inorganic ions activate a number of enzymes; some enzymes (metallothermic) generally inactive, if no one or another specific for this enzyme ion. Lots of enzymes responsible for localization and activation of the enzyme substrate in the process, known as the active centers of enzymes. In the formation of the active center participate specific amino acid residues of the protein molecules, sulfhydryl groups and prosthetic group, if available. So, part of the enzymes that bears the group name flavoproteins, as prosthetic group includes flavins derived (usually flavine adenine dinucleotide - FAD). Easily oxidized and recovering, flavins prosthetic group function biological vectors of hydrogen, such as dehydration amino acids with participation of oxygen or dehydration with participation of cytochromes in the mitochondria of the initial components of the respiratory chain (such as the succinate, choline, Sarkozy and others). Similar functions and other respiratory pigments (hemoglobin and myoglobin - the higher animals and man, and hemerythrin, aristrocracy, hemocyanin and others - lower animals). All these enzymes combines the presence of the active centre of atoms of metal (iron or copper).