In:
European Journal of Biochemistry, Wiley, Vol. 202, No. 3 ( 1991-12), p. 889-896
Abstract:
The enantiomers (+) and (−)‐2,2‐difluorocitrate have been synthesized. Both are good inhibitors of ATP‐citrate lyase, showing competitive inhibition against citrate, with K is = 0.7 μM for (+)‐2,2‐difluorocitrate and 3.2 μM for (−)‐2,2‐difluorocitrate. The inhibition patterns with either ATP or CoA as the varied substrate were uncompetitive and mixed, respectively, but with much weaker inhibition constants. Neither isomer undergoes carbon‐carbon bond cleavage as a substrate and there is no evidence of irreversible time‐dependent inactivation. When ATP‐citrate lyase is incubated with CoA and difluorocitrate, the maximal intrinsic ATPase rate is 10% of the citrate‐induced rate for the (+)‐enantiomer and 2% for the (−)‐enantiomer. 19 F‐NMR studies confirm that only the (+)‐enantiomer is chemically processed. The effects of the difluorocitrate enantiomers on the reaction catalysed by aconitase were examined. (−)‐2,2‐Difluorocitrate is a competitive inhibitor against citrate ( K is = 1.5 μM), whereas the (+)‐enantiomer is a relatively poor mixed inhibitor ( K i 〉 300 μM). The (−)‐enantiomer irreversibly inactivates aconitase at 1.1 min ‐1 · mM ‐1 at 25°C and pH 7.4, whereas no irreversible inhibition is seen with the (+)‐enantiomer. Therefore, it would be expected that the (+)‐enantiomer would slow the rate of acetyl‐CoA synthesis in vivo , without inhibiting the citric acid cycle.
Type of Medium:
Online Resource
ISSN:
0014-2956
,
1432-1033
DOI:
10.1111/ejb.1991.202.issue-3
DOI:
10.1111/j.1432-1033.1991.tb16448.x
Language:
English
Publisher:
Wiley
Publication Date:
1991
detail.hit.zdb_id:
1398347-7
detail.hit.zdb_id:
2172518-4
SSG:
12
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