| Budget Amount *help |
¥6,800,000 (Direct Cost: ¥6,800,000)
Fiscal Year 1994: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1993: ¥5,000,000 (Direct Cost: ¥5,000,000)
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| Research Abstract |
Lipoyl AMP : N^E-lysine lipoyltransferase (lipoyltransferase) catalyzes the transfer of the lipoyl group from lipoyl-AMP to the lysine residue of the specific enzyme proteins. We purified and characterized two isoforms of lipoyltransferase termed lipoyltransferase I and lipoyltransferase II from bovine liver mitochondria. Lipoyltransferase II was purfied to apparent homogeneity whereas the final product of lipoyltransferase I still contained a minor contaminant. Although the two forms could be resolved on a hydroxylapatite column chromatography, they were indistinguishable, as judged by : (a) behavior during purification on ion exchange, hydrophobic, or affinity columns : (b) molecular mass determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel exclusion chromatography (40kDa) ; and (c) catalytic properties (substrate specificity ; kinetic constants ; and optimal pH). Both lipoyltransferase I and II could not use lipoic acid plus MgATP as a substrate in place of lipoyl-AMP.Surprisingly, the lipoyltransferases transferred not only the lipoyl group but also the acyl groups from hexanoyl-, octanoyl-, and decanoyl-AMP to apo-H-protein to a similar extent. In a preliminary experiment, we found that both lipoyltransferase I and II could catalyze transfer of lipoyl moiety to apolipoyl domains of acyltransferaces of pyruvate, alpha-ketoglutarate, and branched-chain alpha-keto acid dehydrogenase complexes produced by the in vitro transcription-translation reaction.
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