Download 20.2 Classification of Enzymes

20.2 Classification of Enzymes
Enzyme names describe the
compound or the reaction
that is catalyzed.
The ribbon structure for
alanine transaminase, an
aminotransferase, contains
495 amino acid residues.
Learning Goal Classify enzymes
and give their names.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Names of Enzymes
The name of an enzyme
• usually ends in ase.
• identifies the reacting substance; for example,
sucrase catalyzes the reaction of sucrose.
• describes the function of the enzyme; for example,
oxidases catalyze oxidation.
• can be a common name, particularly for the
digestive enzymes, such as pepsin and trypsin.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Enzyme Class, Oxidoreductases
The Enzyme Commission of the International Union of
Biochemistry and Molecular Biology systematically classifies
enzymes according to the six general types of reactions they
catalyze (Table 20.2).
Core Chemistry Skill Classifying Enzymes
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Enzyme Classes, Transferases, Hydrolases
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Enzyme Classes, Lyases, Isomerases
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Enzyme Classes, Ligases
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
Match the type of reaction with an enzyme.
1) aminase
2) dehydrogenase
3) isomerase
4) synthetase
A.
B.
C.
D.
converts a cis fatty acid to a trans fatty acid
removes two H atoms to form a double bond
combines two molecules to make a new compound
adds NH3
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Match the type of reaction with an enzyme.
1) aminase
2) dehydrogenase
3) isomerase
4) synthetase
3
2
4
1
A.
B.
C.
D.
converts a cis fatty acid to a trans fatty acid
removes two H atoms to form a double bond
combines two molecules to make a new compound
adds NH3
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chemistry Link to Health:
Isoenzymes As Diagnostic Tools
Isoenzymes
• are different forms of an enzyme that catalyze the same
reaction in different cells or tissues of the body.
• have quaternary structures with slight variations in the
amino acids in the polypeptide subunits.
There are five isoenzymes of lactate dehydrogenase (LDH)
that catalyze the conversion between lactate and pyruvate.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chemistry Link to Health:
Isoenzymes As Diagnostic Tools
Myocardial infarction may be
indicated by an increase in
the levels of creatine kinase
(CK) and lactate
dehydrogenase (LDH).
The different forms of an
enzyme allow a medical
diagnosis of damage or
disease to a particular organ
or tissue.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chemistry Link to Health:
Isoenzymes As Diagnostic Tools
The different isoenzymes of
lactate dehydrogenase
(LDH) indicate damage to
different organs in the body.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.