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(1) In biology, the base—an object or substance—to which sedentary animals and plants, including microorganisms, are attached.
(2) In biochemistry, a substance acted upon by enzymes. The term “substrate” refers to the primary and intermediate products of metabolism (metabolites) that take part in enzymatic transformations. Chemically, substrates may vary from simple molecules of hydrogen peroxide (H2O2) to highly complex molecules of proteins and nucleic acids.
During an enzymatic reaction, the substrate is activated and combines with the enzyme to form an enzyme-substrate complex, which decomposes and releases the products of the reaction. As a rule, a given enzyme activates only few substrates, a phenomenon called substrative specificity. Consequently, the name of a substrate is often the source for the name of the corresponding enzyme. For example, the enzyme that splits D-glucose-1-phosphate into glucose and phosphate is called D-glucose-1-phosphatase.
The substrative specificity of enzymes is determined by the structure of their active centers; substrates can directly affect the formation of these centers. The concentration of substrates is a factor in the regulation of enzymatic activity. Substrates and their analogues—substances similar in structure to the substrates —often induce the biosynthesis of the corresponding enzymes. Some analogues of substrates are specific inhibitors of enzymes.
(3) In microbiology, nutrient media for the growth of microorganisms.
N. N. CHERNOV