BPP-5a is the short member of the bradykinin-potentiating peptide series from the venom of Bothrops jararaca. The supplied sequence is a pyroglutamyl pentapeptide ending in proline, the C-terminal proline being the feature the whole series shares and the one that medicinal chemistry eventually abstracted into captopril. Its pharmacology turns out not to be reducible to ACE inhibition. Ianzer and colleagues reported that BPP-5a produces a potent and long-lasting antihypertensive effect that is nitric oxide dependent, a duration that is difficult to reconcile with a short peptide acting only by occupying the enzyme, and the finding has driven interest in additional targets for this member of the series. Work on the series as a whole showed that these peptides inhibit the two catalytic domains of somatic ACE with differing site specificity rather than blocking both equally, so the shorter and longer members are not simply more and less potent versions of one another. For a laboratory choosing between members of this series, BPP-5a is the reagent of interest when the question concerns nitric-oxide-dependent vascular responses or activity that persists beyond the expected window for simple enzyme occupancy. Where the goal is instead to reproduce the classical ACE-inhibition pharmacology that led to captopril, the nonapeptide BPP-9a (LT1139) is the closer match. | 