C1 - SECTION 2. ENZYME NOMENCLATURE AND CLASSIFICATION Flashcards
Classifications of Enzymes - Based on
catalytic activity of an enzyme
categorized enzymes into six (6) classes
The International Union of Biochemistry (IUB) Enzyme Commission
Older names: Dehydrogenases & Oxidases
Oxidureductase
Catalyze oxidation-reduction reactions
Oxidureductase
catalyze the transfer of electrons from one molecule (the oxidant) to another molecule (the reductant).
Oxidureductase
catalyze reactions similar to the following: A– + B → A + B– where A is the oxidant and B is the reductant
Oxidureductase
Assayed for investigation of cardiac & liver disorders
Oxidureductase
Move an intact group of atoms (NH2 or PO4) from one molecule to another
Transferases
catalyze reactions similar to the following A + BX = AX + B
Transferases
Gives information about liver damage
Transferases
Splits molecules with water as part of the reaction process
Hydrolases
catalyze reactions similar to the following: L A + H20 = B + C
Hydrolases
Three (3) Groups:
o Esterases: ACP, ALP, Lipase
o Peptidases: Leucine aminopeptidase, Pepsin
o Glycosidases: Amylase, Amylo-1,6-glucosidase
o Esterases:
ACP, ALP, Lipase
o Peptidases:
Leucine aminopeptidase, Pepsin
o Glycosidases:
Amylase, Amylo-1,6-glucosidase
Responsible for splitting molecules or breaking of bonds (C to C; C to O; C to N, etc.)
Lyases
catalyze reactions similar to the following: A = B + C
Lyases
Assayed in disorders of skeletal muscles
Lyases
Responsible for the conversion of one isomer to another
Isomerases
catalyze reactions similar to the following: A > B
Isomerases
All reactions are reversible
Isomerases
Enzymes causing bond formation between two molecules to form a larger molecule
Ligases
catalyze reactions similar to the following: A + B = AB
Ligases
Enzymes are classified according to the
type of reaction they catalyze.
In naming an enzyme, the suffix (?) is added to the name of the substrate
“ase”
Describes the nature of the reaction catalyzed
Systematic name
Numerical code designation prefixed w/ the letters E.C.
Systematic name
Example: E.C. 3.1.3.1 = ALP and E.C. 3.1.3.2 = ACP
Systematic name
1st digit =
denotes the class of the enzyme
2nd digit =
sub-class of the enzyme
3rd digit = sub sub-class
4th digit =
specific serial number
a.k.a Non- specific, Practical name, Working name
Trivial name
Uses acronyms and abbreviations
Trivial name
Examples: SGOT, SGPT
Trivial name
ENZYME NOMENCLATURE BASIS
- Type of reaction catalyzed
- Suffix “ASE” added to the name of substrate
- STANDARD SYSTEM
STANDARD SYSTEM
Formulated by
IUB and IUPAC
•This approach removes all ambiguity about the enzyme’s identity
STANDARD SYSTEM
Several distinct forms of enzymes
ENZYME VARIANTS
Important in the diagnosis of specificity
ENZYME VARIANTS
Multichained enzymes of similar activity
ISOENZYMES
Appear in specific tissue, organ & cell organelle of similar organisms
ISOENZYMES
Appear in specific tissue, organ & cell organelle of similar organisms
ISOENZYMES
ISOENZYMES Example:
Lactate Dehydrogenase (LDH)
•Lactate Dehydrogenase (LDH)
Contains [?] (polypeptide chains)
H & M sub-units
- heart, RBC & renal tubules
H4 (LD1)
- heart, RBC & renal tubules
H3M (LD2)
- lungs, lymphocytes, spleen, pancreas
H2M2 (LD3)
- liver, skeletal muscles
HM3 (LD4)
- liver, skeletal muscles
M4 (LD5)
CHARACTERISTICS OF ISOENZYMES
– rate of migration isoenzymes in electrophoresis
1.Electrophoretic mobility
Based on size, molecular weight, type of media used, number of electrons, charge of molecule
1.Electrophoretic mobility
– type of separation technique
Mobility in Ion Exchange Resin
– can be in the form of a chemical substance
Response to Inhibition
- inhibited by 2% Formalin
ACP (RBC)
- not inhibited by 2% Formalin
ACP (Prostate)
is less sensitive to a-naphthyl PO4
ACP (RBC)
Enzymes of similar catalytic activity but are specie specific
HETEROENZYMES
Genetically-transmitted enzyme
ALLOENZYMES
Main importance: Forensic medicine and Genetics
ALLOENZYMES
Important in defining the biochemical characteristics of an individual
ALLOENZYMES
•Generally secreted
PLASMA-SPECIFIC ENZYMES
•Enzymes that exert their function in plasma
PLASMA-SPECIFIC ENZYMES
•Ex. Enzymes associated with the coagulation pathway and complement system
PLASMA-SPECIFIC ENZYMES
•No specific functions in plasma (lack of activators or coenzymes)
NON-PLASMA SPECIFIC ENZYMES
— secreted in plasma at a high rate but rapidly disposed off to excretory channels; transient high conc
•B.1 Enzymes of Secretion
– carry out their functions within the cells in which they are formed
•B.2. Enzymes associated w/ Cellular Metabolism
Ex. ACP (Prostate) only induces in the prostate; CK induces in the heart muscle
•B.2. Enzymes associated w/ Cellular Metabolism
•Found only in one lodation, particularly the cell sap (vacuoles – serves as storage compartment)
UNILOCULAR ENZYME
•Found in the mitochondria & cell sap
BILOCULAR ENZYME