Enzymes

Enzymes

1. Proteins

   • Globular protein has specific 3D shape/tertiary structure. Shape comes from protein's primary structure (specific sequence of amino acids that form protein) + secondary structure.
   • In globular proteins, final 3D shape usually has hydrophobic amino acid R-groups in centre of 'ball', + hydrophilic amino acid R-groups around outside of ball. Amino acid chain spirals, pleats + turns to form overall structure.
   • All enzymes v. similar in many ways:
     • Globular proteins - generally soluble in water
     • Act as catalysts - speeding up chemical reactions, but not being 'used up' as part of reaction.
     • Specific - catalysing reaction involving only 1 type of substrate.
     • Globular structure contains 'pocket'/cleft area called active site.
     • Activity affected by temp + pH.

2. Active Site

   • Enzymes relatively large molecules, consisting of 100s of amino acids. Vast majority of amino acids involved in maintaining specific tertiary structure of enzyme.
     • Enzyme function related to shape. For any enzyme to work properly, tertiary structure must be maintained in v. specific way.
   • Whole primary, secondary + tertiary structure of enzymes involved in achieving v. specific shape for active site.
     • Active site: Area of enzyme where catalytic activity of enzyme occurs.
   • Each enzyme has v. specific, individual active site shape, maintained by v. specific overall tertiary structure. V. few amino acids form actual active site. As active site shape of enzyme is v. specific + individual - means reaction an enzyme can catalyse is also v. specific + individual.

3. Catalysts

   • Enzymes often referred to as biological catalysts. Speed up chemical reactions. Industrial + commercially used catalysts include some metals + other chemicals, but in comparison with enzymes - often slow.
   • Led to branch of biotechnology to investigate + use enzymes in industrial processes to replace such inorganic catalysts. Added advantage of enzymes are they're specific to 1 catalytic reaction + don't produce range of unwanted by-products.
   • How many enzymes?
     • V. many chemical reactions occurring within (sometimes outside) cell catalysed by enzymes. Metabolism can be described as enzyme-driven.
     • Each of processes of formation + breakage of bonds requires at least 1 specific enzyme in order to catalyse reaction. Processes of protein synthesis, digestion, respiration + photosynthesis each require no. of enzymes.
     • Each catalysts specific reaction in sequence of events that make up process. Estimated that an individual cell may contain over 1000 different enzymes.

4. Substrate + Product

   • Chemical reaction that's catalysed by enzyme, substrate is turned into product. E.g. if we use enzyme e.g. maltase, to catalyse conversion of maltose to glucose, then substrate maltose is converted to product glucose.
     • maltose → glucose + glucose
   • Name given to enzyme usually derived from substrate of reaction that's catalysed, with suffix '-ase'.