Substance P synthesis by enzymatic fragment condensation using product–directed antibodies as molecular traps

This paper describes the enzyme catalyzed synthesis of the undecapeptide substance P from its non‐associated fragments (1–7) and (8–11) or (1–8) and (9–11). The fragment condensation was mediated by the use of product specific antibodies as molecular traps. As catalyst a previously purified endopeptidase was used which specifically hydrolyzes substance P at the Phe 7 –Phe 8 and Phe 8 –Gly 9 bonds. The synthesis was performed in analytical scale and product formation was guided by reversed phase HPLC combined with radioimmunoassay. It appeared that the substance P fragments (1–8) and (9–11) were condensed to a larger extent than (1–7) and (8–11). This observation may well result from the higher affinity of the antibodies observed for substance P (8–11) as compared to that found for the other fragments. Increased concentration of the antibodies also seemed to result in enhanced resynthesis of substance P.