SUBSTANCE-P INACTIVATING ENZYMES IN HUMAN CEREBROSPINAL-FLUID

The K-m and V-max values were determined for enzymes in human lumbar cerebrospinal fluid (CSF) that inactivate synthetic substance P(SP = RPKPQQFFGLM-NH2) and produce metabolic products. For the human limbar CSF samples analyzed in this study, K-m = 2.24 +/- 0.93 mM and V-max = 0.113 +/- 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 peptices, 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).