ABSTRACT
A novel lipoxygenase (BLOX) was purified from black soybean (Glycine max (L.) Merr.), and its catalytic properties were characterized. The molecular weight of BLOX was 101â¯kDa and its unique heterodimeric structure with two different subunits of molecular weight 46â¯kDa and 55â¯kDa was elucidated. The optimum pH and temperature of BLOX were pH 9.5 and 40⯰C, respectively. BLOX was highly stable at the pH range of 6.0-10.0 and below 40⯰C, and was stimulated by adding ferrous ion (Fe2+). In terms of substrate specificity, BLOX showed a substrate preference to linoleic acid that is the main substance to produce hydroperoxides in soybean. When it reacted with linoleic acid, the major product was 13(S)-hydroperoxy-9,11-octadecadienoic acid; therefore, it could be classified into the linoleate 13S-LOX family (EC 1.13.11.12). Finally, the kinetic parameters (Vmax, Km, and kcat) of BLOX were 0.124â¯mMâ¯min-1, 0.636â¯mM, and 12.28 s-1, respectively, and consequently, the catalytic efficiency (kcat/Km) was calculated as 1.93â¯×â¯104 M-1·s-1. These catalytic characteristics of BLOX could contribute to understanding the enzymatic rancidification of black soybean, and to further biotechnical approaches to control and mitigate the deterioration.