Evidence that oleoyl-CoA and ATP-dependent elongations coexist in rapeseed (Brassica napus L.).
The elongation of different substrates was studied using several subcellular fractions from Brassica napus rapeseed. In the presence of malonyl-CoA, NADH and NADPH, very-long-chain fatty acid (VLCFA) synthesis was observed from either oleoyl-CoA (acyl-CoA elongation) or endogenous primers (ATP-dependent elongation). No activity was detected using oleic acid as precursor. Acyl-CoA and ATP-dependent elongation activities were mainly associated with the 15 000 g/25 min membrane fraction. Reverse-phase TLC analysis showed that the proportions of fatty acids synthesized by these activities were different. Acyl-CoA elongation increased up to 60 microM oleoyl-CoA, and ATP-dependent elongation was maximum at 1 mM ATP. Both activities increased with malonyl-CoA concentration (up to 200 microM). Under all conditions tested, acyl-CoA elongation was higher than ATP-dependent elongation, and, in the presence of both ATP and oleoyl-CoA, the elongation activity was always lower. ATP strongly inhibited acyl-CoA elongation, whereas ATP-dependent elongation was slightly stimulated by low oleoyl-CoA concentrations (up to 15 microM) and decreased in the presence of higher concentrations. CoA (up to 150 microM) had no effect on the ATP-dependent elongation, whereas it inhibited the acyl-CoA elongation. These marked differences strongly support the presence in maturing rapeseed of two different elongating activities differently modulated by ATP and oleoyl-CoA.
Domergue
F
F
Laboratoire de Biogenèse Membranaire, Université Victor Segalen Bordeaux 2, France Ecole Supérieure de Technologie des Biomolécules de Bordeaux (ESTBB), Université Victor Segalen Bordeaux 2, France.
Chevalier
S
S
Santarelli
X
X
Cassagne
C
C
Lessire
R
R
D000214:Acyl Coenzyme A / Q000378:metabolism* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D001937:Brassica / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D004883:Erucic Acids / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis; D007700:Kinetics; D008316:Malonyl Coenzyme A / Q000378:metabolism / Q000494:pharmacology
D000214:Acyl Coenzyme A; D004883:Erucic Acids; D005227:Fatty Acids; C049811:erucic acid; C017585:oleoyl-coenzyme A; D008316:Malonyl Coenzyme A; D000255:Adenosine Triphosphate