Enzyme Kinetics

Today’s Objectives: (To learn and understand)

•Basics of Enzymes

•Nomenclature of Enzymes

•Commercial Application of Enzymes

• Simple Enzyme Kinetics

What are Enzymes?

• Enzymes are biological catalysts that are protein molecules in nature.

• All metabolic processes in the cell need enzymes in order to occur at rates

fast enough to sustain life.

• Like any other catalysts, they increase the rate of reaction without

themselves undergoing permanent chemical changes.

• The catalytic ability of enzymes is due to its particular protein structure.

Structure of Enzymes

Structure of Glucosidase Enzyme

Nomenclature of Enzymes

•Nondescriptive names (rennin, pepsin, trypsin) doesn’t give any idea about source, function or reaction catalyzed by the enzyme.• Systematic naming convention

• adding the suffix -ase to the name of the substrate with which the enzyme functions, or to the reaction that is catalyzed

• Examples• Lactase, Lipase, Maltase …• Alcohol dehydrogenase, glucose isomerase, glucose oxidase ...

Enzyme Commission

•The nomenclature was determined by the Enzyme Commission in 1964.•Enzymes are classified into six main classes according to the reaction

being catalyzed. •Each class will contain subclasses which in turn contain subclasses as

well.•All enzymes are assigned an “EC” code.

Partial outline of EC major classes

•EC 1. Oxidoreductases• 1.1 Acting on = CH-OH group of substrates• 1.1.1 Requires NAD+ or NADP+ as hydrogen acceptor• 1.1.1.1. Specific substrate is ethyl alcohol

•EC 2. Transferases • 2.1. Transfer of methyl groups 2.2 . Transfer of glycosyl groups

•EC 3. Hydrolases •EC 4. Lyases •EC 5. Isomerases •EC 6. Ligases

EC 1. Oxidoreductases

•Catalyze the transfer of hydrogen or oxygen atoms or electrons from one substrate to another, also called oxidases, dehydrogenases, or reductases. Since these are redox reactions, an electron donor/acceptor is also required to complete the reaction.

EC 2. Transferases

•Catalyze group transfer reactions, excluding oxidoreductases. These are of the general form: A-X + B ↔ BX + A

EC 3. Hydrolases

•Catalyze hydrolytic reactions. Includes lipases, esterases, nitrilases, peptidases/proteases. These are of the general form:

A-X + H2O ↔ X-OH + HA

EC 4. Lyases•Catalyze non-hydrolytic removal of functional groups from

substrates, often creating a double bond in the product; or the reverse reaction, i.e, addition of function groups across a double bond.

A-B → A=B + X-Y X Y• Includes decarboxylases and aldolases in the removal direction, and

synthases in the addition direction.

EC 5. Isomerases

•Convert a molecule from one isomer to another. Isomerases can either facilitate intramolecular rearrangements in which bonds are broken and formed or they can catalyze conformational changes.

EC 6. Ligases

•Catalyzes the synthesis of various (mostly C-X) bonds, coupled with the breakdown of energy-containing substrates, usually ATP

Industrial Application of Enzymes

•Enzymes are usually made by microorganisms grown in a pure culture or obtained directly from plants and animals.

Industry Enzyme class ApplicationDetergent Protease, Lipase, Amylase Stain removal

Food Protease, Lipase, Lactase Dairy productsFats and oils Lipase, phospholipase Transesterification

Enzyme Kinetics

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Effect of substrate concentration on the initial reaction rate

Change of product and substrateconcentrations with respect to time

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