title: LKPNM: a prodrug-type ACE-inhibitory peptide derived from fish protein.
abstract: It has been previously documented that the thermolysin-digest of "Katsuo-bushi", a Japanese traditional food processed from dried bonito possesses potent inhibitory activity against angiotensin I-converting enzyme (ACE). The present authors isolated eight kinds of ACE-inhibitory peptides from it. Of these isolated peptides, LKPNM (IC50 = 2.4 microM) was found to be hydrolyzed by ACE to produce LKP (IC50 = 0.32 microM) with 8-fold higher ACE-inhibitory activity relative to the parent peptide or LKPNM, suggesting that LKPNM can be regarded as a prodrug-type ACE-inhibitory peptide. For assessment of relative antihypertensive activities of LKPNM and LKP to that of captopril, they were orally administered to SHR rats to monitor time-course changes of blood pressures, whereby it was evidenced that both LKPNM and captopril showed maximal decrease of blood pressure 4 h after oral administration and their efficacies lasted until 6 h post-administration. In sharp contrast, however, maximal reduction of blood pressure occurred as early as 2 h after administration of LKP. Minimum effective doses of LKPNM, LKP and captopril were 8, 2.25 and 1.25 mg/kg, respectively. When compared on molar basis, antihypertensive activities of LKPNM and LKP accounted for 66% and 91% relative to that of captopril, respectively, whereas in vitro ACE-inhibitory activities of LKPNM and LKP were no more than 0.92% and 7.73% compared with that of captopril (IC50 = 0.022 microM). It is of interest to note that both of these peptides exert remarkably higher antihypertensive activities in vivo despite weaker in vitro ACE-inhibitory effects, which was ascertained by using captopril as the reference drug.
authors.affiliation: Nippon Synthetic Chemical Industry, Osaka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Fujita
authors.forename: M
authors.initials: M
authors.lastname: Yoshikawa
mesh_terms: D000284:Administration, Oral; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D000959:Antihypertensive Agents / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology; D002216:Captopril / Q000008:administration & dosage; D002645:Chickens; D005396:Fish Products / Q000032:analysis*; D006801:Humans; D007275:Injections, Intravenous; D009124:Muscle Proteins / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D009842:Oligopeptides / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D011355:Prodrugs / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D013820:Thermolysin / Q000378:metabolism
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D000959:Antihypertensive Agents; D009124:Muscle Proteins; D009842:Oligopeptides; D011355:Prodrugs; D002216:Captopril; D013820:Thermolysin