Application of the multiple antigenic peptides (MAP) strategy to the production of prophormone convertases antibodies: Synthesis, characterization and use of 8‐branched immunogenic peptides

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Abstract
Antiserum against an N‐terminal sequence of murine prohormone convertase‐1 (mPC1) incorporating the sequence immediatley following the junction between the putative pro‐region and the active enzyme was obtained. This was accomplished using the multiple antigenic peptide (MAP) approach whereupon an 8‐branched polylysine core to which are grafted multiple copies of a 16 amino acid peptide representing the N‐terminal sequence of mPC1 (positions 84–99) was synthesized by solid‐phase Fmoc chemistry. The ensuing peptide was purified and fully characterized by RP‐HPLC, 1H‐NMR, amino acid composition, peptide sequencing and ion‐spray mass spectrometry. The immunological properties of the resulting antibodies in detecting recombinant PC1 in both crude and purified preparations were compared with antibodies raised against a similar N‐terminal segment of PC1 but using the conventioanl method of peptide–carrier protein conjugation and also developed against a C‐terminal fusion protein of PC1. Our data indicate that the MAP antibody was as efficient as both the amino and carboxy‐terminal antibodies in qualitative as well as quantitative analysis of PC1 encoded protein by radioimmunoassay. Following an identical approach, antibodies against other prohormone convertases like furin, PC5/6 and PACE4 were also developed and subsequently applied to a number of biochemical and immunological studies. In each case, the ease of preparation and high immunogenicity of the MAP approach were confirmed and reside in the simplicity and rapidity with which a potent and useful antiserum is obtained.