Peptide natural role

The natural role of peptide deformylases (EC 3.5.1.31) is the hydrolysis of the N-terminal formyl group from nascent peptides. This enzyme combines a good... 

Mason AJ, Evans BA, Cox DR, Shine J, Richards RI. Structure of mouse kallikrein gene family suggests a role in specific processing of biologically active peptides. Nature 1983 303 300-307. 

Both FASs and PKSs are structurally and mechanistically related to another class of multifunctional enzymes called nonribosomal peptide synthetases. These enzymes activate amino acids as aminoacyl thioesters, which subsequently undergo condensation via formation of amide bonds, leading to biosynthesis of peptide natural products. Enzyme-bound phosphopantetheinyl groups also play a central role in the peptide assembly process. For comparison, the genetics and biochemistry of peptide synthetases are also briefly reviewed here. 

Peptides are long, continuous and unbranched chain polymers formed by the polymerisation of amino acid monomers. During the polymerisation process two units are linked together via a peptide bond (-CO-NH-), which is formed by the reaction of a carboxylic group (-COOH) of one amino acid and an amino group (-NHi) of another. Peptides naturally occur in animals and plants, and can also be synthesised in the laboratory. Peptides play a significant role in the prevention of bacterial infections and, to date, more than 5,000 antimicrobial peptides (AMP) have been discovered or synthesised. 

Fig. 8. De novo designed a-hehcal proteins. Dimers of the amphiphilic helix-forming peptide a B, GELEELLKKLKELLKG (see Table 1), in which the nature of the linker connecting the individual heflces plays a critical role in the stmcture of the final protein, (a) Using a Pro residue as the linker, ie, a B-Pro-a B, three molecules aggregated to form a trimeric coded-cod. (b) Using Pro-Arg-Arg as the linker, ie, a B-Pro-Aig-Arg-a, resulted in the...

Relatively few heteroaromatic N-oxides occur in nature. The chemistry of compounds that contain the oxidized peptide bond (the so-called hydroxamic acids) and their role in iron metabolism have been reviewed (67SC1443). Another review deals with the natural occurrence of N-oxides (68MI1). 

This effect is particularly well documented for y - and -amino acid residues [217, 218] which in several natural products (bleomycin A2 [219], calyculins [220]) have been shown to play a substantial role in the pre-organization of the whole molecule into its bioactive conformation. For example, changes in the substitution pattern of the y-amino acid linker in bleomycin A2 result in reduced DNA cleavage efficiency [219]. In the case of y-peptides, changing the relative configuration like or unlike of y " -amino acids has been used as a strategy to generate different local conformations (Fig. 2.34) suitable either for the construction of helices [201] or turns ]202-204]. 

A further important group of derivatives is that of amino acids activated by phosphoric acid or its esters. In nature, phosphorylation processes play an important activating role in peptide and protein synthesis. 

Solubilities and stabilities of calcium phosphates in natural waters have been described (735), as have the nucleation and growth of calcium phosphate from solution (736). Several species have long been known to inhibit the precipitation of calcium phosphates, for example carbohydrates (646) and statherin, the tyrosine-rich peptide which occurs in saliva (737). The role of... 

---