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Enzymes

• Enzymes are biocatalysts?Catalysts of life
• A catalyst is defined as a substance that increases the velocity or the rate of a chemical reaction, without itself undergoing any change in the process
• Enzymes are biocatalysts that are synthesized by living cells.
• They are proteinaceous (exception is the ribozyme, which is an RNA), colloidal, and thermolabile (inactive at 0?C and destroyed at 100?C)
• They are specific in action, catalyze all biochemical reactions and are susceptible to many factors like temperature, pH, etc.
• Examples: urease, carbonic anhydrase, pepsin, rennin, etc.

Antienzymes

• Antienzymes are those substances which when injected in the body produces certain molecules, which act as inhibitors and inhibits the function of the enzyme, related to that particular reaction
• Examples: Antitrypsin, antirennin, antipepsin, etc.

Substrate

• The substrate is a substance upon which an enzyme acts and gets converted into the corresponding product
• For example, maltose is the substrate over which the enzyme maltase acts to from glucose

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Characteristics of Enzymes

• Colloidal nature
• They are of great size
• Their molecular weights usually range from 12000 to over a million Daltons
• Hence, they are very large compared to their substrates or the functional group they act upon
• The molecular weight of many enzymes are found to be approximately n-fold (n is an integer) multiple of 17500, which is found to be a unit in most proteins
• On account of their large size, the enzyme molecules possess extremely low rates of diffusion and forms colloidal systems in water
• Due to their giant size, the enzymes exhibit many colloidal properties such as:
• Diffusion rates are very slow
• May produce considerable high light scattering. They form turbidity in solution known as Tyndall effect
• Catalytic nature
• A universal feature of all enzymatic reactions is the virtual absence of any side product
• An enzyme is precisely adapted to catalyze a particular reaction. For example, amylase catalyzes the breakdown of starch
• They act catalytically and accelerate the rate of chemical reactions, occurring in the plant and animal tissues
• They normally do not participate in the reaction, or if they do so, at the end of the reaction, they are recovered as such without undergoing any qualitative or quantitative change
• This is why they are capable of catalyzing the transformation of a large quantity of substrate
• Thus, the catalytic potency of enzymes is extremely great
• Turnover number
• The catalytic power of an enzyme is measured by the turnover number or the molecular activity
• It is defined as the number of substrate molecules converted into the product in a given unit of time by a single enzyme molecule, when the enzyme is fully saturated with the substrate
• The turnover number of some enzymes are given as follows:

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