Secondary Metabolites Flashcards
When are secondary metabolites most often produced?
During the stationary phase of growth after standard growth has finished
What are two common examples of secondary metabolites?
- Polyketides
- Non-ribosomal polypeptides
What produces polyketides?
Actinomycetes (bacteria) and fungi
What is a protein domain?
A region of a protein’s polypeptide chain that is self-stabilizing and that folds independently from the rest. Domains often have different catalytic or binding activities.
What is a protein module?
Where several protein domains come together in part of a protein (collection of domains doing a particular biochemical job)
What is the starting point of a polyketide?
2C or 3C (Acetyl-CoA or Propionyl-CoA)
How does the chain length only increase by 2C if 3C units are added?
CO2 is lost after each addition
What enzyme is responsible for the addition of 3C subunits?
Polyketide Synthase (PKS)
What are some properties of type 1 PKS enzymes?
- Very large single protein with one or more modules with multiple domains
- Form more complex polyketides
- Much more common
- Eukaryotic or prokaryotic
What are some properties of type 2 PKS enzymes?
- Several smaller polypeptides, each with a specific domain, which catalyse successive stages of polyketide synthesis when coming together, normally as quaternary protein
- Simpler polyketides
- They will fold to form their own domain
- Bacterial
What drugs are used to lower cholesterol?
Statins
What makes non-ribosomal peptides unique?
Produced by both bacteria and fungi which feature a polypeptide chain with peptide bonds but which are not made by the classical ribosomal pathway
What produces them?
Non-ribosomal synthetases (products tend to be smaller than ones built by ribosomes)
What is the make-up of NRPS?
- Very large proteins composed of a series of modules, each with 2-4 specific domains with particular catalytic ability
- Similar organisation to type 1 PKS enzymes
- Each module adds a specific amino acid (7 modules = 7 amino acids added)
