الانزيمات

Enzymes are biologic polymers that catalyze the chemical reactions

all reactions in the body are mediated by enzymes, which are protein catalysts that increase the rate of reactions without being changed in the overall process. Among the many biologic reactions that are energetically possible, enzymes selectively channel reactants (called substrates) into useful pathways. Enzymes thus direct all metabolic events.
NOMENCLATURE
There are two type of nomenclatures
Recommended name
Most commonly used enzyme names have the suffix "-ase" attached to the substrate of the reaction (for example, glucosidase, urease, sucrase), or to a description of the action performed (for example, lactate dehydrogenase and Glucokinase). [Note: Some enzymes retain their original trivial names, which give no hint of the associated enzymic reaction, for example, trypsin and pepsin.
B. Systematic name
The International Union of Biochemistry and Molecular Biology (IUBMB) developed a system of nomenclature in which enzymes are divided into six major classes as shown in the Figure, each with numerous subgroups.
PROPERTIES OF ENZYMES
Enzymes are protein catalysts that increase the velocity of a chemical reaction, and are not consumed during the reaction they catalyze.
Most enzyme-catalyzed reactions are highly efficient, proceeding from 1000 to 108 times faster than uncatalyzed reactions. Typically, each enzyme molecule is capable of transforming 100 to 1000 substrate molecules into product each second.

Active sites
Enzyme molecules contain a special pocket or cleft called the active site. The active site contains amino acid side chains that create a three-dimensional surface complementary to the substrate (Figure 5.2). The active site binds the substrate, forming an enzyme-substrate (ES) complex. ES is converted to product and enzyme again that can react immediately with another substrate molecule
FACTORS AFFECTING REACTION VELOCITY
Enzymes can be isolated from cells, and their properties studied in a test tube, in Different enzymes show different responses to changes in substrate concentration, temperature, and pH. This section describes factors that influence the reaction velocity of enzymes. Enzymic responses to these factors give us valuable clues as to how enzymes function in living cells