Effects of sodium dodecyl sulphate on enhancement of lipoxygenase activity of hemoglobin.

Lipoxygenases comprise a family of non-heme iron-containing enzymes that catalyze the stereospecific dioxygenation of polyunsaturated fatty acids with 1, 4-cis-cis-pentadiene structure. Hemoglobin, a heme iron-containing protein has been reported to have lipoxygenase activity but the assay conditions that could enhance the activity remain obscure. Therefore, establishment of optimum assay conditions for lipoxygenase activity of hemoglobin could allow modeling of hemoglobin as lipoxygenase. Hemoglobin was extracted from blood of an identified individual of genotype AA. The hemoglobin was dialyzed at 4 degrees C for 24 h against 50 mM Tris-HCl buffers (pH 8.5 and 7.2) and effects of sodium dodecyl sulphate (SDS) and linoleic studied at pH 5.0 and 7.2 with UV-VIS Titration Spectrophotometry. The results show that 3.3, 8.6 and 88.1% concentrations of met-hemoglobin were found in presence of 0.0 mM SDS at pH 5.0 and 7.2, 1.043 mM SDS at pH 7.2 and 0.404 mM SDS at pH 5.0 respectively. Also, the difference spectra of hemoglobin in presence of linoleic acid showed positive peak at 285 nm which suggest the presence of oxodienes--a reaction product of hydroperoxidase activity of lipoxygenase. Formation of met-hemoglobin/met-myoglobin is highly correlated with lipid oxidation. Since highest concentration of met-hemoglobin (88.1%) was observed in presence of 0.404 mM SDS at pH 5.0, lipoxygenase activity of hemoglobin was enhanced in presence of SDS under these conditions.