Introduction to Enzymes and Their History

Enzyme Introduction

• Enzymes are proteins
• They catalyze biochemical reactions
• They have a globular shape
• Enzymes are complex 3-D structures

Historical Perspectives

• Biochemistry history intertwined with enzyme research
• Enzymes first recognized in animal food digestion, sugar fermentation, and yeast processes
• Enzymes initially thought to be inseparable from living cells, like yeast.
• Eduard Buchner discovered that yeast extracts could ferment sugar to alcohol (demonstrating the concept of non-living enzymes)
• James Sumner and John Northrop later established that all enzymes are proteins and won the Nobel Prize.
• Later, catalytic RNA, also known as ribozymes, were discovered in the 1980s.

Enzyme Nomenclature

• Enzyme names often end in "-ase"
• Enzyme names often describe the enzyme's function (e.g., sucrase catalyzes sucrose hydrolysis)
• Some enzyme names describe both substrate and function (e.g., alcohol dehydrogenase oxidizes ethanol)
• Some enzymes use common names (e.g. pepsin, trypsin)

Enzyme Classification

• Enzymes classified into six classes by the International Union of Biochemists (IUB)
• Classification based on reactions catalyzed.
• Classes include:
  • Oxidoreductases
  • Transferases
  • Hydrolases
  • Lyases
  • Isomerases
  • Ligases
• Each enzyme has a unique classification number (e.g., EC:(2.7.1.1) HEXOKINASE)

Enzyme Properties

• Catalytic Efficiency: Enzymes are highly efficient, significantly speeding up reactions compared to uncatalyzed reactions.
• Specifity: Highly specific, interacting with particular substrates and catalyzing a single type of reaction
  • Absolute specificity: catalyze only one reaction
  • Relative specificity: includes Group (e.g, amino), Bond (e.g., type of bond), Stereospecificity (e.g., specific isomer)
• Mild Reaction Conditions: Operate under mild conditions (e.g., 37°C, physiological pH).

Enzyme Active Site

• The shape and chemical environment of the active site determine catalytic function

Enzyme Examples and Functions

• Oxidoreductases: Involved in oxidation-reduction reactions (e.g., lactate dehydrogenase). Examples include oxidases, peroxidases, and dehydrogenases
• Transferases: Transfer functional groups between molecules (e.g., transaminases, kinases).
• Hydrolases: Hydrolyze various chemical bonds by adding water atoms across chemical bonds (e.g. amylases, phosphatases). This includes peptidases, carbohydrases (like amylase, maltase, lactase), lipid hydrolyzing enzymes, deaminases.
• Lyases: Cleave various bonds by means that are not hydrolysis and oxidation. This includes fumarase, carbonic anhydrase.
• Isomerases: Catalyze isomerization changes within a single molecule by isomerizations(e.g. L-to-D).
• Lyases: Many other examples including aldehydes, alcohols, and other types of functional groups.
• Ligases/Synthases: Join two molecules through covalent bonds, using energy from ATP (e.g. glutamine synthetase)
• Synthases: Biosynthetic reactions that don't use energy from ATP

Enzyme Purification

• Preparation for further study.

Additional Notes

• Enzymes are essential for life, and their specific role and function are crucial in numerous biochemical processes.
• Many enzymes are called synthetases; however, some enzymes that catalyze biosynthetic reactions belong to classes other than ligases, called synthases.