Selective mechanism-based inactivation of peptidylglycine alpha-hydroxylating monooxygenase in serum and heart atrium vs. brain.
Peptidylglycine alpha-hydroxylating monooxygenase (PHM; EC 1.14.17.3) catalyses the rate-limiting step in the post-translational activation of substance P, among other neuropeptides, from its glycine-extended precursor. Comparative kinetic studies were performed, using trans-styrylacetic acid or trans-styrylthioacetic acid as known mechanism-based inhibitors, of PHM isolated from rat, horse or human blood serum. Distinctive species differences with respect to PHM inactivation were observed: the efficiency of inactivation decreased in the order of horse >> rat > human. Trans-styrylacetic acid was more active than its thioether derivative. Moreover, we studied the differential sensitivity towards mechanism-based inactivation, of soluble PHM from rat blood serum and rat brain by trans-styrylacetic acid or benzylhydrazine, as well as the membrane-associated enzymes from rat brain and heart atrium. For the heart atrium membrane PHM or the soluble PHM from blood serum, inactivation rate constants k(inact)/K(I) of approximately 100 M(-1)sec(-1) were found with trans-styrylacetic acid. However, neither of the two tested compounds, at 100 microM or 12 mM, respectively, could inactivate the soluble or membranous PHMs from rat brain during a 15-min pre-incubation period. Instead, under conditions of reversible inhibition, trans-styrylacetic acid competitively inhibited the soluble or membrane-associated brain PHM with inhibition constants K(I) = 0.6 microM and 1.0 microM, respectively. Organ-selective, time-dependent inactivation of PHM with compounds of the above types might be an important pharmacological tool to control peripheral neuropeptide activation.
Bolkenius
F N
FN
Marion Merrell Research Institute, Strasbourg, France.
Ganzhorn
A J
AJ
Chanal
M C
MC
Danzin
C
C
D000818:Animals; D001921:Brain / Q000201:enzymology*; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D006325:Heart Atria; D006736:Horses; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors* / Q000097:blood; D009097:Multienzyme Complexes; D009206:Myocardium / Q000201:enzymology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity; D013373:Substance P / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000494:pharmacology
D005229:Fatty Acids, Monounsaturated; D006834:Hydrazines; D009097:Multienzyme Complexes; D013438:Sulfhydryl Compounds; C107647:styrylthioacetic acid; C064180:4-phenyl-3-butenoic acid; D013373:Substance P; C006730:benzylhydrazine; D006899:Mixed Function Oxygenases; C035189:peptidylglycine monooxygenase