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Human liver paraoxonase (PON1): Subcellular distribution and characterization
Author(s) -
Gonzalvo Maria C.,
Gil Fernando,
Hernandez Antonio F.,
Rodrigo Lourdes,
Villanueva Enrique,
Pla Antonio
Publication year - 1998
Publication title -
journal of biochemical and molecular toxicology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.526
H-Index - 58
eISSN - 1099-0461
pISSN - 1095-6670
DOI - 10.1002/(sici)1099-0461(1998)12:1<61::aid-jbt8>3.0.co;2-n
Subject(s) - paraoxonase , paraoxon , chemistry , pon1 , enzyme , aryldialkylphosphatase , microsome , calcium , biochemistry , enzyme assay , incubation , ionic strength , substrate (aquarium) , acetylcholinesterase , biology , ecology , organic chemistry , aqueous solution , genotype , gene
The subcellular localization and different biochemical properties of a human hepatic microsomal enzyme that hydrolyses paraoxon (paraoxonase, PON1) were studied and compared to the paraoxon hydrolase activity found in human plasma as well as in rat liver and plasma. Having evaluated the influence of the postmortem interval by a parallel experiment performed in rats, we conclude that the paraoxonase activity was preferentially localized in the microsomal fraction. The enzyme reaction was optimized according to temperature, pH, buffer, ionic strength, substrate concentration, and enzyme protein concentration. The characterization of human liver paraoxonase included the study of optimum pH, pH stability, heat inactivation assays, and kinetic parameters ( K m and V max ). In addition, the enzyme activity showed an absolute requirement for exogenous calcium. The activity was lost after incubation with EDTA and partially restored by the addition of calcium; however, other metals assayed were not able to activate the human liver enzyme as did calcium. Our results support the possible identity between human plasma and liver paraoxonases. In spite of the technical difficulties of this study and the possible interference of the postmortem changes in the results, this article represents the first systematic approach to the characterization of human liver paraoxonase. © 1997 John Wiley & Sons, Inc. J Biochem Toxicol 12: 61–69, 1998