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The interaction of acyl-CoA with acyl-CoA binding protein and carnitine palmitoyltransferase I
The affinity of recombinant rat acyl-CoA binding protein (ACBP) towards acyl-CoAs was investigated using both fluorimetric analysis and isothermal titration microcalorimetry, neither of which requires the physical separation of bound and free ligand for determining the dissociation constants ( K d)....
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Published in: | The international journal of biochemistry & cell biology 2001-08, Vol.33 (8), p.807-815 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Get full text |
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Summary: | The affinity of recombinant rat acyl-CoA binding protein (ACBP) towards acyl-CoAs was investigated using both fluorimetric analysis and isothermal titration microcalorimetry, neither of which requires the physical separation of bound and free ligand for determining the dissociation constants (
K
d). The displacement of 11-(dansylamino)undecanoyl-CoA (DAUDA-CoA) from ACBP yielded binding parameters for the competing acyl-CoAs that compared favourably with those obtained using ultra-sensitive microcalorimetric titration. The
K
d values of ACBP for oleoyl-CoA and docosahexaenoyl-CoA are 0.014 and 0.016 μM, respectively. Under identical experimental conditions, carnitine palmitoyltransferase I (CPT I) of purified rat liver mitochondria has
K
d values of 2.4 and 22.7 μM for oleoyl-CoA and docosahexaenoyl-CoA, respectively. Given that CPT I was not only present at a much lower concentration but also has an appreciably lower affinity for acyl-CoAs than ACBP, it is proposed that CPT I is capable of interacting directly with ACBP-acyl-CoA binary complexes. This is supported by the fact that the enzyme activity correlated with the concentration of ACBP-bound acyl-CoA but not the free acyl-CoA. A transfer of acyl-CoA from ACBP-acyl-CoA binary complexes to CPT I could be a result of the enzyme inducing a conformational alteration in the ACBP leading to the release of acyl-CoA. |
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ISSN: | 1357-2725 1878-5875 |
DOI: | 10.1016/S1357-2725(01)00049-8 |