**2.4 Nonribosomal polypeptides**

They come under the class of peptide secondary metabolites produced by microorganisms such as bacteria, cyanobacteria, fungi, and symbionts of higher eukaryotes. The nonribosomal peptides (NRPs) are synthesized by multidomain mega-enzymes named nonribosomal peptide synthetases (NRPSs), without the need for the cell ribosomal machinery and messenger RNAs. Their bioactivity and pharmaceutical properties can be evidenced by antibiotics (e.g., actinomycin, penicillin, cephalosporin, vancomycin), cytotoxics (e.g., bleomycin), and immunosuppressants (e.g., cyclosporines), which have found immense importance in the clinical industry [12].

### **2.5 Enzyme cofactors**

The analysis of the cofactors is imperative in order to gain the understanding of the enzyme catalyzed reactions. Enzymes are proteins that catalyze vast repertoire of reactions found in nature. Generally the enzymes are composed 20 amino acid residues, but some may also require additional small molecules in the active site for the catalysis reaction to occur, these small molecules are known as cofactors. The cofactor can be a metal ion (e.g., Fe+) or small organic molecule [13].
