Phosphorus-Containing Inhibitors of Proteolytic Enzymes

Abstract

The dipeptidyl peptidase IV (DP IV, EC 3.4.14.5) is a proline specific serine protease, which cleaves Xaa-Pro dipeptides from the N-terminus of oligoand polypeptides (for review Lambeir et al 2003). During the last years our attention was directed to the development of DP IV inhibitors and their specificity. It is well-known, that Xaa-Pro dipeptides which are products of substrate hydrolysis are competitive inhibitors of DP IV (Rahfeld 1989). Furthermore, the product analogous amino acid pyrrolidides (Pyrr), e.g. 1 (figure 1), and thiazolidides are also known as potent competitive inhibitors (Born et al 1994). Previously, we synthesized thioxo amino acid amides as amide bond isosteres of amino acid pyrrolidides and thiazolidides (Stockel-Maschek et al 2000a). Moreover, analogous phosphonamidates 2 were synthesized as amide bond isosteres (figure 1). Peptides containing a 3-amino-2-hydroxy acid like bestatin and amastain were described as inhibitors of different aminopeptidases (Umezawa et al 1976, Nishizawa et al 1977, Rich et al 1984). Peptides and amides containing a N-terminal 3-amino-2-hydroxy acid and a penultimate proline or proline-analogous structure were described as the first potent inhibitors of aminopeptidase P (APP) (Prechel et al 1995; Stockel et al 1997). Recently, we showed, that these 3-amino-2-hydroxy acid containing APP inhibitors (3, figure 1) are also able to inhibit other aminopeptidases and dipeptidyl peptidase IV (Stockel-Maschek et al in preparation). In a further study, the carbonyl group of the 3-amino-2-hydroxy acid was replaced by a tetrahedral phosphorus moiety. The concept of transition-state analogues has been very useful in designing potent inhibitors of proteolytic enzymes. Tetrahedral phosphorus derivatives are stable mimics of a tetrahedral intermediate that lies along the proteolytic reaction coordinate. Thus, we have synthesized 2-amino-1-hydroxy phosphonic acid derived amides and peptides (compounds 4, figure 1). The title compounds were tested as inhibitors of the aminopeptidases APP, aminopeptidase M (APM), leucine aminopeptidase (LAP) as well as DP IV.