Substance P inactivating enzymes in human cerebrospinal fluid

Abstract

The K m and V max values were determined for enzymes in human lumbar cerebrospinal fluid (CSF) that inactivate synthetic substance P ( SP = RPKPQQFFGLM-NH 2 ) and produce metabolic products. For the human lumbar CSF samples analyzed in this study, K m = 2.24 ± 0.93 mM and V max = 0.113 ± 0.035 nmol/ml/min ( n = 10; mean ± SEM) for the rate of decrease of SP. HPLC analysis of the incubated synthetic peptide fragments demonstrated that the primary enzymatically produced fragment is SP(3–11), with minor amounts in decreasing order of SP(1–4), SP(1–7), and SP(1–9). Electrospray ionization mass spectrometry (ESI-MS) confirmed the appropriate molecular weights for the four peptides, SP(3–11), SP(1–4), SP(1–7), and SP(1–9). These data demonstrate that the primary enzyme in human lumbar CSF that acts on synthetic SP is a post-proline cleaving enzyme (PPCE).