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Questions and Answers
What type of bonds can be broken by hydrolases?
What type of bonds can be broken by hydrolases?
What is the systematic name of the enzyme that breaks down acetyl choline?
What is the systematic name of the enzyme that breaks down acetyl choline?
What type of enzyme is aldolase?
What type of enzyme is aldolase?
What type of isomers can be produced by isomerases?
What type of isomers can be produced by isomerases?
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What is the result of the action of ligases?
What is the result of the action of ligases?
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What is the difference between synthetase and synthase?
What is the difference between synthetase and synthase?
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What is the purpose of the IUBMB system of nomenclature of enzymes?
What is the purpose of the IUBMB system of nomenclature of enzymes?
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What is the suffix added to the substrate to form the name of an enzyme?
What is the suffix added to the substrate to form the name of an enzyme?
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What is the function of oxidoreductases?
What is the function of oxidoreductases?
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What is the EC number for the enzyme Alcohol dehydrogenase?
What is the EC number for the enzyme Alcohol dehydrogenase?
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What is the systematic name of the enzyme Hexokinase?
What is the systematic name of the enzyme Hexokinase?
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How many major classes of enzymes are there according to the IUBMB system?
How many major classes of enzymes are there according to the IUBMB system?
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What is the function of transferases?
What is the function of transferases?
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What does the first digit in the EC number represent?
What does the first digit in the EC number represent?
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Study Notes
Classification of Enzymes
- Early enzymes were given whimsical names, such as Pepsin, Trypsin, and Chymotrypsin, which are still used today.
- Later, enzymes were named by adding the suffix "-ase" to the substrate, for example, Lactase acts on lactose to form glucose and galactose.
IUBMB System of Classification
- The International Union of Biochemistry and Molecular Biology (IUBMB) developed a system of nomenclature for enzymes in 1964, modified in 1972 and 1978.
- The system uses a four-digit code starting with EC (enzyme class), followed by:
- First digit: class
- Second digit: subclass
- Third digit: sub-subclass or subgroup
- Fourth digit: number of the particular enzyme in the list
Six Major Classes of Enzymes
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Class 1: Oxidoreductases
- Catalyze oxidation of one substrate with simultaneous reduction of another substrate or co-enzyme
- Example: Alcohol dehydrogenase (Alcohol-NAD-oxidoreductase; EC.1.1.1.1)
-
Class 2: Transferases
- Transfer one group (other than hydrogen) from the substrate to another substrate
- Example: Hexokinase (ATP-Hexose-6-phosphatetransferase)
-
Class 3: Hydrolases
- Hydrolyze ester, ether, peptide, or glycosidic bonds by adding water
- Example: Acetyl choline esterase or Acetyl choline hydrolase
-
Class 4: Lyases
- Remove groups from substrates or break bonds by mechanisms other than hydrolysis
- Example: Aldolase
-
Class 5: Isomerases
- Produce optical, geometric, or positional isomers of substrates
- Example: Triose phosphate isomerase
-
Class 6: Ligases
- Link two substrates together, usually with simultaneous hydrolysis of ATP
- Example: Acetyl CoA carboxylase
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Description
Learn about the history of enzyme naming, from early whimsical names to the modern IUBMB system of classification. Understand how enzymes are named based on their substrates and functions.
