CCHM 322 Enzymology Part I Quiz

Enzymology Overview

• Enzymology is the study of enzymes and their roles in biological processes.
• Clinically significant enzymes help diagnose diseases based on their levels in the blood.
• Enzymes are proteins that catalyze biochemical reactions, enhancing reaction rates.

Enzyme Characteristics

• Enzymes bind substrates at an active site, forming an enzyme-substrate (ES) complex.
• The allosteric site is another area on the enzyme that can influence activity without binding the substrate.
• Enzymes can only catalyze specific reactions based on their structure and the nature of their substrates.

Types of Specificity

• Absolute specificity: Enzyme interacts with only one specific substrate.
• Group specificity: Enzyme interacts with all substrates that have a particular chemical group.
• Bond specificity: Enzyme acts on substrates with a specific type of chemical bond.
• Stereoisomeric specificity: Enzyme interacts with substrates that are specific optical isomers.

Factors Influencing Enzymatic Reactions

• Substrate and enzyme concentration: Michaelis-Menten kinetics; reaction rates depend on the concentration of substrates and enzymes.
• Saturation kinetics: Maximum reaction rate is reached when the enzyme is fully saturated with substrates.
• pH levels: Enzymes have an optimal pH (7.0-8.0); extreme pH can deactivate enzymes.
• Temperature: Increased temperatures generally increase reaction rates up to a point (optimum around 37°C), beyond which enzymes denature.

Inhibitors

• Inhibitors interfere with enzymatic activity.
  • Competitive inhibition: Inhibitors compete with the substrate for the active site.
  • Non-competitive inhibition: Inhibitors bind to an allosteric site, altering enzyme activity.
  • Uncompetitive inhibition: Inhibitors bind the ES complex, preventing a reaction.

Temperature and Storage

• Enzymes are preserved at various temperatures:
  • Long-term storage at -20°C.
  • Short-term storage in the refrigerator (2-8°C).
  • Room temperature (15-30°C) for labile enzymes.
• Avoid repeated freezing and thawing to prevent enzyme inactivation.

Enzyme Structure

• Enzymes consist of amino acids, forming complex structures:
  • Primary structure: Specific sequence of amino acids.
  • Secondary structure: Twisting of polypeptide chains.
  • Tertiary structure: Three-dimensional folding of secondary structures.
  • Quaternary structure: Combination of multiple tertiary structures.

Isoenzymes

• Isoenzymes are variants of enzymes that catalyze the same reaction but differ in physical properties.
• Examples include creatine kinase isoenzymes:
  • CK1 (CKBB) - Brain
  • CK2 - Heart
  • CK3 (CKMM) - Muscle

Nomenclature and Classification

• Enzymes are classified based on their activity and reaction types established by the Enzyme Commission (E.C.):
  • Oxidoreductases: Oxidation-reduction reactions.
  • Transferases: Transfer of groups other than hydrogen.
  • Hydrolases: Hydrolysis reactions.
  • Lyases: Removal of groups without hydrolysis.
  • Isomerases: Isomerization reactions.
  • Ligases: Joining of substrates with energy expenditure.

Important Notes

• Enzymatic elevation in blood indicates cell damage or disease presence.

• Understanding enzyme characteristics and factors influencing their activity is essential for clinical diagnostics.### Enzymes and Their Classifications

• Lactate Dehydrogenase (LDH)

  • Systematic Name: L-Lactate: NAD+
  • Abbreviation: LDH
  • Enzyme Classification: 1.1.1.27, oxidoreductase

• Glucose-6-phosphate Dehydrogenase (G-6-PDH)

  • Systematic Name: D-Glucose-6-phosphate: NADP
  • Abbreviation: G-6-PD
  • Enzyme Classification: 1.1.1.49, oxidoreductase

• Glutamate Dehydrogenase (GLD)

  • Systematic Name: L-Glutamate: NAD(P)
  • Abbreviation: GLD
  • Enzyme Classification: 1.4.1.3, oxidoreductase and deaminase

Aminotransferases

• Aspartate Aminotransferase (AST)

  • Systematic Name: L-Aspartate: 2-oxoglutarate aminotransferase
  • Abbreviation: GOT (glutamate oxaloacetate transaminase)
  • Enzyme Classification: 2.6.1.1

• Alanine Aminotransferase (ALT)

  • Systematic Name: L-Alanine: 2-oxoglutarate aminotransferase
  • Abbreviation: GPT (glutamate transaminase)
  • Enzyme Classification: 2.6.1.2

Kinases and Transferases

• Creatine Kinase (CK)

  • Systematic Name: Creatine phosphokinase
  • Abbreviation: CPK
  • Enzyme Classification: 2.7.3.2

• Gamma-Glutamyl Transferase (GGT)

  • Systematic Name: (5-Glutamyl) peptide: amino acid-5-glutamyltransferase
  • Abbreviation: GGPT
  • Enzyme Classification: 2.3.2.2

• Glutathione-S-Transferase (GST)

  • Systematic Name: Glutathione transferase
  • Abbreviation: a-GST
  • Enzyme Classification: 2.4.1.18

• Glycogen Phosphorylase (GP)

  • Systematic Name: Orthophosphate-a-D-glucosyltransferase
  • Abbreviation: GP
  • Enzyme Classification: 2.4.1.1

Other Enzyme Classes

• Pyruvate Kinase (PK)

  • Systematic Name: Pyruvate kinase
  • Abbreviation: PK
  • Enzyme Classification: 2.7.1.40

• Alkaline Phosphatase (ALP)

  • Systematic Name: Orthophosphoric monoester phosphohydrolase (alkaline optimum)
  • Abbreviation: ALP
  • Enzyme Classification: 3.1.3.1

• Acid Phosphatase (ACP)

  • Systematic Name: Orthophosphoric monoester phosphohydrolase (acid optimum)
  • Abbreviation: ACP
  • Enzyme Classification: 3.1.3.2

• Alpha-Amylase (AMY)

  • Systematic Name: 1,2-D-Glucan gluconohydrolase
  • Abbreviation: AMS
  • Enzyme Classification: 3.2.1.1

• Chymotrypsin

  • Systematic Name: Chymotrypsin
  • Abbreviation: CHY
  • Enzyme Classification: 3.1.21.1

• Trypsin

  • Systematic Name: Trypsin
  • Abbreviation: TRY
  • Enzyme Classification: 3.4.21.4

Isomerases and Lyases

• Aldolase

  • Systematic Name: D-D-Fructose-1,6-bisdiphosphate D-glyceraldehyde-3-phosphate-lyase
  • Abbreviation: ALD
  • Enzyme Classification: 4.1.2.13

• Triosephosphate Isomerase (TPI)

  • Systematic Name: Triose-phosphate isomerase
  • Abbreviation: TPI
  • Enzyme Classification: 5.3.1.1

• Glutathione Synthase

  • Systematic Name: Glutathione synthase
  • Abbreviation: GSH-S
  • Enzyme Classification: 6.3.2.3