Isolation and Some Characteristics of Lipoxygenase from Aromatic Brown Rice (Oryza Sativa L.) cv. Khao Dawk Mali 105

Abstract

Lipoxygenase from Khao Dawk Mali 105 aromatic brown rice was isolated by extracting brown rice liquid nitrogen powder using 0.2 M phosphate buffer pH 7, fractionating with 30–60% (NH₄)₂SO₄, dialyzing and gel filtration on Sephadex G-200. The optimum pHs for dialyzed lipoxygenase activity were around 7.5 and 9.5. The enzyme appeared to be completely inactivated after heating 30 min at 70°C, 20 min at 80°C and 10 min at 90°C. The enzyme could be inhibited by MgCl₂, ZnCl₂, KCl, BHA, vitamin E, vitamin C, and BHT; however, CaCl₂ acted as the enzyme activator.

Keywords:

• Aromatic brown rice
• Characteristics
• Inhibition
• Isolation
• Khao Dawk Mali 105
• Lipoxygenase

ACKNOWLEDGMENTS

The authors would like to express sincere gratitude to the Kasetsart University Research and Development Institute (KURDI), Thailand for some financial support. The authors also would like to thank for Patum Rice Mill and Granary Public Co., Ltd., Thailand in kindly providing rice samples for the research. Special thanks to Dr. Dwayne Meadows for correcting the English grammar and Miss Kunnikar Boonsiripiphat for artwork preparation.

Notes

^a Based on isolation from 40 g liquid nitrogen powder (values are means of 3 replications).

^b Relative to lipoxygenase activity in crude extract.

^c Based on specific activity of crude extract.