Question

Not all naturally occurring peptides are synthesized by ribosomes that decode messenger RNA. How does non-ribosomal peptide synthesis take place? How does it differ from polyketide synthesis? What are some functions of these peptides?

Short answer

Non-ribosomal peptide synthesis takes place with the help of a class of enzymes called non-ribosomal peptide synthetase. It differs from polyketide synthesis as this occurs with the help of a different class of enzyme known as polyketide synthases. Non-ribosomal peptides promote the initiation, elongation, and termination of polypeptide chain formation.

Step-by-step solution

Non-ribosomal proteins

Non-ribosomal proteins are a group of proteinaceous secondary metabolic products that are not synthesized by ribosomes but by a class of enzymes called non-ribosomal peptide synthetase. They are thereby independent of messenger RNA. These are usually found in prokaryotes. Every enzyme synthesizes only one type of peptide.

Polyketides

Polyketides are also a large group of secondary metabolites that are found in prokaryotes like cyanobacteria.The biosynthesis of polyketide shares some characteristics; however, one major difference is the class of enzymes being used in their synthesis. In polyketide synthesis, the class of enzyme called polyketide synthases is used.

Functions of non-ribosomal peptides

Non-ribosomal peptides or proteins help promote polypeptide chain initiation, elongation, and termination. They also function as many natural products such as antibiotics and immunosuppressants.