Reaction of rat liver glutathione S-transferases and bacterial dichloromethane dehalogenase with dihalomethanes
Blocki, FA; Logan, MS; Baoli, C; Wackett, LP
HERO ID
730517
Reference Type
Journal Article
Year
1994
Language
English
PMID
| HERO ID | 730517 |
|---|---|
| In Press | No |
| Year | 1994 |
| Title | Reaction of rat liver glutathione S-transferases and bacterial dichloromethane dehalogenase with dihalomethanes |
| Authors | Blocki, FA; Logan, MS; Baoli, C; Wackett, LP |
| Journal | Journal of Biological Chemistry |
| Volume | 269 |
| Issue | 12 |
| Page Numbers | 8826-8830 |
| Abstract | Dichloromethane dehalogenase from Methylophilus sp. DM11 is a glutathione S-transferase homolog that is specifically active with dihalomethane substrates. This bacterial enzyme and rat liver glutathione S-transferases were purified to investigate their relative reactivity with CH2Cl2 and related substrates. Rat liver alpha class glutathione transferases were inactive and mu class enzymes showed low activity (7-23 nmol/min/mg of protein) with CH2Cl2. theta class glutathione transferase 5-5 from rat liver and Methylophilus sp. dichloromethane dehalogenase showed specific activities of > or = 1 mumol/min/mg of protein. Apparent Kcat/Km were determined to be 3.3 x 10(4) and 6.0 x 10(4) L M-1 S-1 for the two enzymes, respectively. Dideutero-dichloromethane was processed to dideutereo-formaldehyde, consistent with a nucleophilic halide displacement mechanism. The possibility of a GSCH2X reaction intermediate (GS, glutathione; X, halide) was probed using CH2ClF to generate a more stable halomethylglutathione species (GSCH2F). The reaction of CH2ClF with dichloromethane dehalogenase produced a kinetically identifiable intermediate that decomposed to formaldehyde at a similar rate to synthetic HOCH2CH2SCH2F. 19F-NMR revealed the transient formation of an intermediate identified as GSCH2F by its chemical shift, its triplet resonance, and H-F coupling constant consistent with a fluoromethylthioether. Its decomposition was matched by a stoichiometric formation of fluoride. These studies indicated that the bacterial dichloromethane dehalogenase directs a nucleophilic attack of glutathione on CH2Cl2 to produce a halomethylthioether intermediate. This focuses attention on the mechanism used by theta class glutathione transferases to generate a halomethylthioeter from relatively unreactive dihalomethanes. |
| Pmid | 8132617 |
| Wosid | WOS:A1994NB41100034 |
| Url | <Go to ISI>://WOS:A1994NB41100034 |
| Is Certified Translation | No |
| Dupe Override | No |
| Is Public | Yes |
| Language Text | English |
| Is Qa | No |