title: In vitro kinetics of soybean lipoxygenase with combinatorial fatty substrates and its functional significance in off flavour development.
abstract: Lipoxygenase (Lox) mediated oxidation of polyunsaturated fatty acids (PUFA) in mature soya seeds results in objectionable flavour. In the present study, Lox isozymes were purified to near homogeneity (107-fold). Lox-2 and 3 displayed remarkable kinetic preference (1.7 and 1.5-fold, respectively) for low PUFA ratios (LA/LeA) (PRs) among the selected PUFA combinations. Lox-1 displayed no specific preference. Pure Lox-1 displayed unbiased response towards substrates with marginal preference (1.2-fold) for linoleic acid at its optimum pH. Volatile compounds profiling showed a direct relationship between PRs and hexanal to trans-2-hexenal (1.47, 2.24 and 18.90 for 2, 7 and 15 PRs, respectively) ratio. The off-flavour determining parameters like TBA value, carbonyl value and lipid hydroperoxides (LHPODs) exhibited significant negative correlation (0.76, 0.74, 0.72; p<0.0001) in selected soya genotypes displaying varied PRs and significant positive correlation (0.89, 0.81. 0.89; p<0.0001) with ratio of PI (polyene index) to PRs - suggesting the plausible significance of PUFA ratios in biological lipid peroxidation.
authors.affiliation: Division of Biochemistry, Indian Agricultural Research Institute, New Delhi 110012, India. Electronic address: somnathmandal@jncasr.ac.in.
authors.forename: Somnath
authors.initials: S
authors.lastname: Mandal
authors.forename: Anil
authors.initials: A
authors.lastname: Dahuja
authors.forename: Abhijit
authors.initials: A
authors.lastname: Kar
authors.forename: I M
authors.initials: IM
authors.lastname: Santha
mesh_terms: D005231:Fatty Acids, Unsaturated / Q000737:chemistry / Q000378:metabolism*; D005421:Flavoring Agents / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008084:Lipoxygenase / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D012639:Seeds / Q000737:chemistry / Q000201:enzymology; D013025:Glycine max / Q000737:chemistry / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D005231:Fatty Acids, Unsaturated; D005421:Flavoring Agents; D010940:Plant Proteins; D008084:Lipoxygenase
keywords: Lipid peroxidation; Lipoxygenase isozymes; PUFA ratio; Soya off flavour