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Senescence marker protein‐30 is a unique enzyme that hydrolyzes diisopropyl phosphorofluoridate in the liver
Author(s) -
Kondo Yoshitaka,
Ishigami Akihito,
Kubo Sachiho,
Handa Setsuko,
Gomi Keiko,
Hirokawa Kozo,
Kajiyama Naoki,
Chiba Tsuyoshi,
Shimokado Kentaro,
Maruyama Naoki
Publication year - 2004
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2004.06.028
Subject(s) - chemistry , tabun , diisopropyl fluorophosphate , paraoxon , biochemistry , enzyme , acetylcholinesterase , nerve agent
Senescence marker protein‐30 (SMP30) was originally identified as a novel protein in the rat liver, the expression of which decreases androgen‐independently with aging. We have now characterized a unique property of SMP30, the hydrolysis of diisopropyl phosphorofluoridate (DFP), which is similar to the chemical warfare nerve agents sarine, soman and tabun. Hydrolysis of DFP was stimulated equally well by 1 mM MgCl 2 , MnCl 2 or CoCl 2 , to a lesser extent by 1 mM CdCl 2 but not at all by 1 mM CaCl 2 . No 45 Ca 2+ ‐binding activity was detected for purified SMP30, suggesting that SMP30 is not a calcium‐binding protein, as others previously stated. Despite the sequence similarity between SMP30 and a serum paraoxonase (PON), the inability of SMP30 to hydrolyze PON‐specific substrates such as paraoxon, dihydrocoumarin, γ‐nonalactone, and δ‐dodecanolactone indicate that SMP30 is distinct from the PON family. We previously established SMP30 knockout mice and have now tested DFPase activity in their livers. The livers from wild‐type mice contained readily detectable DFPase activity, whereas no such enzyme activity was found in livers from SMP30 knockout mice. Moreover, the hepatocytes of SMP30 knockout mice were far more susceptible to DFP‐induced cytotoxicity than those from the wild‐type. These results indicate that SMP30 is a unique DFP hydrolyzing enzyme in the liver and has an important detoxification effect on DFP. Consequently, a reduction of SMP30 expression might account for the age‐associated deterioration of cellular functions and enhanced susceptibility to harmful stimuli in aged tissue.