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A characteristic Glu17 residue of pig carnitine palmitoyltransferase 1 is responsible for the low K m for carnitine and the low sensitivity to malonyl‐CoA inhibition of the enzyme
Author(s) -
Relat Joana,
PujolVidal Magdalena,
Haro Diego,
Marrero Pedro F.
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06774.x
Subject(s) - malonyl coa , carnitine , carnitine o palmitoyltransferase , enzyme , chemistry , carnitine palmitoyltransferase i , amino acid , biochemistry , biology , endocrinology , medicine , beta oxidation
Human carnitine palmitoyltransferase 1B (CPT1B) is a highly malonyl‐CoA‐sensitive enzyme (IC50 = 0.097 μ m ) and has a positive determinant (residues 18–28) of malonyl‐CoA inhibition. By contrast, rat carnitine palmitoyltransferase 1A is less sensitive to malonyl‐CoA inhibition (IC 50 = 1.9 μ m ), and has both a positive (residues 1–18) and a negative (residues 18–28) determinant of its inhibition. Interestingly, pig CPT1B shows a low degree of malonyl‐CoA sensitivity (IC 50 = 0.804 μ m ). Here, we examined whether any additional molecular determinants affect malonyl‐CoA inhibition of CPT1B. We show that the malonyl‐CoA sensitivity of CPT1B is determined by the length (either 50 or 128 residues) of the N‐terminal region constructed by recombining pig and human enzymes. We also show that the N‐terminal region of pig CPT1B carries a single positive determinant of malonyl‐CoA sensitivity, but that this is located between residues 1 and 18 of the N‐terminal segment. Importantly, we found a single amino acid variation (D17E) relevant to malonyl‐CoA sensitivity. Thus, Asp17 is specifically involved, under certain assay conditions , in the high malonyl‐CoA sensitivity of the human enzyme, whereas the naturally occurring variation, Glu17, is responsible for both the low malonyl‐CoA sensitivity and high carnitine affinity characteristics of the pig enzyme. This is the first demonstration that a single naturally occurring amino acid variation can alter CPT1B enzymatic properties.