Microbial production of thioether-stabilized peptides

This thesis describes the successful biological production and secretion of thioether-stabilized therapeutic peptides. The lantibiotic modification- and transport enzymes NisBTC and LtnM2T involved in the synthesis of the lantibiotics nisin and lacticin 3147, respectively, were exploited for the introduction of thioether bridges in nonlantibiotic peptides. Importantly, thioether peptides produced via lantibiotic enzymes contain only one isomer (DL), whereas chemically induced thioether formation can lead to several stereo isomers (i.e. DL, LL, LD and DD). Exploiting the nisin modification enzymes NisB and NisC, we were able to demonstrate for the first time the posttranslational introduction of a thioether bridge in a therapeutic peptide, an analog of angiotensin-(1-7). This therapeutic peptide variant has a significantly improved stability and the effectivity of its interaction with the angiotensin-(1-7) receptor is even enhanced. This cyclized analog of angiotensin-(1-7) is therefore a promising therapeutic peptide candidate for treatment of cardiovascular diseases. Moreover, other therapeutic peptides may be thioether-stabilized, using lantibiotic synthesis enzymes. By stabilization, these therapeutic peptides are less sensitive to proteolytic breakdown and accordingly need less frequent administration and/or in a lower dose. In addition, stabilization may allow oral and pulmonary delivery. These delivery ways are more patient-friendly than injection. While there are hundreds of medically highly important therapeutic peptides, the pharmaceutical market of already a single therapeutic peptide can have a size of over a billion dollar. Consequently, stabilization of already FDA-approved therapeutic peptide hormones and development of new effective stabilized peptides has a tremendous potential