title: Involvement of human blood arylesterases and liver microsomal carboxylesterases in nafamostat hydrolysis.
abstract: Metabolism of nafamostat, a clinically used serine protease inhibitor, was investigated with human blood and liver enzyme sources. All the enzyme sources examined (whole blood, erythrocytes, plasma and liver microsomes) showed nafamostat hydrolytic activity. V(max) and K(m) values for the nafamostat hydrolysis in erythrocytes were 278 nmol/min/mL blood fraction and 628 microM; those in plasma were 160 nmol/min/mL blood fraction and 8890 microM, respectively. Human liver microsomes exhibited a V(max) value of 26.9 nmol/min/mg protein and a K(m) value of 1790 microM. Hydrolytic activity of the erythrocytes and plasma was inhibited by 5, 5'-dithiobis(2-nitrobenzoic acid), an arylesterase inhibitor, in a concentration-dependent manner. In contrast, little or no suppression of these activities was seen with phenylmethylsulfonyl fluoride (PMSF), diisopropyl fluorophosphate (DFP), bis(p-nitrophenyl)phosphate (BNPP), BW284C51 and ethopropazine. The liver microsomal activity was markedly inhibited by PMSF, DFP and BNPP, indicating that carboxylesterase was involved in the nafamostat hydrolysis. Human carboxylesterase 2 expressed in COS-1 cells was capable of hydrolyzing nafamostat at 10 and 100 microM, whereas recombinant carboxylesterase 1 showed significant activity only at a higher substrate concentration (100 microM). The nafamostat hydrolysis in 18 human liver microsomes correlated with aspirin hydrolytic activity specific for carboxylesterase 2 (r=0.815, p<0.01) but not with imidapril hydrolysis catalyzed by carboxylesterase 1 (r=0.156, p=0.54). These results suggest that human arylesterases and carboxylesterase 2 may be predominantly responsible for the metabolism of nafamostat in the blood and liver, respectively.
authors.affiliation: Department of Hygienic Chemistry, Faculty of Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi, Kanazawa, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yamaori
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Fujiyama
authors.forename: Mika
authors.initials: M
authors.lastname: Kushihara
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Funahashi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kimura
authors.forename: Ikuo
authors.initials: I
authors.lastname: Yamamoto
authors.forename: Tomomichi
authors.initials: T
authors.lastname: Sone
authors.forename: Masakazu
authors.initials: M
authors.lastname: Isobe
authors.forename: Tohru
authors.initials: T
authors.lastname: Ohshima
authors.forename: Kenji
authors.initials: K
authors.lastname: Matsumura
authors.forename: Minoru
authors.initials: M
authors.lastname: Oda
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D000293:Adolescent; D000818:Animals; D001550:Benzamidines; D019556:COS Cells; D002265:Carboxylic Ester Hydrolases / Q000037:antagonists & inhibitors / Q000097:blood / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D006146:Guanidines / Q000493:pharmacokinetics*; D006207:Half-Life; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D008875:Middle Aged; D011994:Recombinant Proteins / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000493:pharmacokinetics*
chemical_list: D001550:Benzamidines; D004791:Enzyme Inhibitors; D006146:Guanidines; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D002265:Carboxylic Ester Hydrolases; C019734:arylesterase; C032855:nafamostat