Abstract
Thirty carbonates, thiocarbonates, carbamates, and carboxylic esters of α-naphthol, β-naphthol, and p-nitrophenol were synthesized and tested as substrates for liver carboxylesterases from the crude microsomal fractions of human and mouse, and purified isozymes, hydrolases A and B, from rat liver microsomes. The carbonates, thiocarbonates, and carboxylic esters of α-naphthol were cleaved more rapidly than the corresponding β-naphthol isomers by the mammalian liver esterases. α-Naphthyl esters of acetic, propionic, and butyric acids were among the best substrates tested for these enzymes. The majority of the substrates was consistently hydrolyzed at higher rates by hydrolase B compared with hydrolase A, although the Michaelis-Menten constant (K(m)) values of selected substrates differed widely with these two isozymes. Malathion was a 15-fold better substrate for hydrolase B than for hydrolase A. Compared with the corresponding carboxylates, the carbonate moiety of α- and β-naphthol and p-nitrophenol lowered the specific activities of the enzymes by about fivefold but improved stability under basic conditions. The optimum pH of mouse liver esterase with the acetate, methylcarbonate, and ethylthiocarbonate of α-naphthol was between pH 7.0 and pH 7.6. Human and mouse liver microsomal esterase activities were about five orders of magnitude lower than the esterase activities of purified rat liver hydrolase B. A relationship between the catalytic activity of the enzymes and the lipophilicity of the naphthyl substrates indicated that (i) in the α- and β-naphthyl carbonate series, an inverse relationship between enzyme activity and lipophilicity of the substrates was observed, whereas (ii) in the α-naphthyl carboxylate series, an increase in enzyme activity with increasing lipophilicity of the substrates up to a logP value of about 4.0 was observed, after which the enzyme activity decreased.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 639-648 |
| Number of pages | 10 |
| Journal | Pharmaceutical Research |
| Volume | 10 |
| Issue number | 5 |
| DOIs | |
| State | Published - 1993 |
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Keywords
- α- and β-naphthyl substrates
- carboxylesterases
- esterase assay, in microtiter plate
- hydrolases A and B
- mammalian liver
- p-nitrophenol substrates
ASJC Scopus subject areas
- Chemistry(all)
- Pharmaceutical Science
- Pharmacology
Cite this
Hydrolysis of carbonates, thiocarbonates, carbamates, and carboxylic esters of α-naphthol, β-naphthol, and p-nitrophenol by human, rat, and mouse liver carboxylesterases. / Huang, T. L.; Szekacs, A.; Uematsu, T.; Kuwano, E.; Parkinson, A.; Hammock, B. D.
In: Pharmaceutical Research, Vol. 10, No. 5, 1993, p. 639-648.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Hydrolysis of carbonates, thiocarbonates, carbamates, and carboxylic esters of α-naphthol, β-naphthol, and p-nitrophenol by human, rat, and mouse liver carboxylesterases
AU - Huang, T. L.
AU - Szekacs, A.
AU - Uematsu, T.
AU - Kuwano, E.
AU - Parkinson, A.
AU - Hammock, B. D.
PY - 1993
Y1 - 1993
N2 - Thirty carbonates, thiocarbonates, carbamates, and carboxylic esters of α-naphthol, β-naphthol, and p-nitrophenol were synthesized and tested as substrates for liver carboxylesterases from the crude microsomal fractions of human and mouse, and purified isozymes, hydrolases A and B, from rat liver microsomes. The carbonates, thiocarbonates, and carboxylic esters of α-naphthol were cleaved more rapidly than the corresponding β-naphthol isomers by the mammalian liver esterases. α-Naphthyl esters of acetic, propionic, and butyric acids were among the best substrates tested for these enzymes. The majority of the substrates was consistently hydrolyzed at higher rates by hydrolase B compared with hydrolase A, although the Michaelis-Menten constant (K(m)) values of selected substrates differed widely with these two isozymes. Malathion was a 15-fold better substrate for hydrolase B than for hydrolase A. Compared with the corresponding carboxylates, the carbonate moiety of α- and β-naphthol and p-nitrophenol lowered the specific activities of the enzymes by about fivefold but improved stability under basic conditions. The optimum pH of mouse liver esterase with the acetate, methylcarbonate, and ethylthiocarbonate of α-naphthol was between pH 7.0 and pH 7.6. Human and mouse liver microsomal esterase activities were about five orders of magnitude lower than the esterase activities of purified rat liver hydrolase B. A relationship between the catalytic activity of the enzymes and the lipophilicity of the naphthyl substrates indicated that (i) in the α- and β-naphthyl carbonate series, an inverse relationship between enzyme activity and lipophilicity of the substrates was observed, whereas (ii) in the α-naphthyl carboxylate series, an increase in enzyme activity with increasing lipophilicity of the substrates up to a logP value of about 4.0 was observed, after which the enzyme activity decreased.
AB - Thirty carbonates, thiocarbonates, carbamates, and carboxylic esters of α-naphthol, β-naphthol, and p-nitrophenol were synthesized and tested as substrates for liver carboxylesterases from the crude microsomal fractions of human and mouse, and purified isozymes, hydrolases A and B, from rat liver microsomes. The carbonates, thiocarbonates, and carboxylic esters of α-naphthol were cleaved more rapidly than the corresponding β-naphthol isomers by the mammalian liver esterases. α-Naphthyl esters of acetic, propionic, and butyric acids were among the best substrates tested for these enzymes. The majority of the substrates was consistently hydrolyzed at higher rates by hydrolase B compared with hydrolase A, although the Michaelis-Menten constant (K(m)) values of selected substrates differed widely with these two isozymes. Malathion was a 15-fold better substrate for hydrolase B than for hydrolase A. Compared with the corresponding carboxylates, the carbonate moiety of α- and β-naphthol and p-nitrophenol lowered the specific activities of the enzymes by about fivefold but improved stability under basic conditions. The optimum pH of mouse liver esterase with the acetate, methylcarbonate, and ethylthiocarbonate of α-naphthol was between pH 7.0 and pH 7.6. Human and mouse liver microsomal esterase activities were about five orders of magnitude lower than the esterase activities of purified rat liver hydrolase B. A relationship between the catalytic activity of the enzymes and the lipophilicity of the naphthyl substrates indicated that (i) in the α- and β-naphthyl carbonate series, an inverse relationship between enzyme activity and lipophilicity of the substrates was observed, whereas (ii) in the α-naphthyl carboxylate series, an increase in enzyme activity with increasing lipophilicity of the substrates up to a logP value of about 4.0 was observed, after which the enzyme activity decreased.
KW - α- and β-naphthyl substrates
KW - carboxylesterases
KW - esterase assay, in microtiter plate
KW - hydrolases A and B
KW - mammalian liver
KW - p-nitrophenol substrates
UR - http://www.scopus.com/inward/record.url?scp=0027318905&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0027318905&partnerID=8YFLogxK
U2 - 10.1023/A:1018987111362
DO - 10.1023/A:1018987111362
M3 - Article
C2 - 8321828
AN - SCOPUS:0027318905
VL - 10
SP - 639
EP - 648
JO - Pharmaceutical Research
JF - Pharmaceutical Research
SN - 0724-8741
IS - 5
ER -