Open AccessMechanism of fatty acid desaturation in the green alga Chlorella vulgaris
Author(s) -
Behrouzian Behnaz,
Fauconnot Laëtitia,
Daligault Franck,
NugierChauvin Caroline,
Patin Henri,
Buist Peter H.
Publication year - 2001
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2001.02258.x
Subject(s) - chlorella vulgaris , kinetic isotope effect , deuterium , linoleic acid , bond cleavage , double bond , fatty acid , chlorella , chemistry , stereochemistry , cleavage (geology) , intermolecular force , biosynthesis , biochemistry , biology , enzyme , organic chemistry , algae , botany , catalysis , molecule , paleontology , physics , quantum mechanics , fracture (geology)
The hypothesis that the Δ 9 desaturase of Chlorella vulgaris might operate by a synchronous mechanism has been tested using a kinetic isotope effect (KIE) approach. Thus the intermolecular primary deuterium KIE on the individual C–H bond cleavage steps involved in Δ 9 desaturation have been determined by incubating growing cultures of C. vulgaris (strain 211/8K) with mixtures of the appropriate regiospecifically deuterated fatty acid analogues. Our analysis shows that the introduction of a double bond between C‐9 and C‐10 occurs in two discrete steps as the cleavage of the C9–H bond is very sensitive to isotopic substitution ( k H / k d = 6.6 ± 0.3) whereas a negligible isotope effect ( k H / k d = 1.05 ± 0.05) was observed for the C10–H bond‐breaking step. Similar results were obtained for linoleic acid biosynthesis (Δ 12 desaturation). These data clearly rule out a synchronous mechanism for these reactions.