Kinetics of Acid Inactivation of Soybean Lipoxygenase and Its Effects on the Functional Properties of Soy Protein

Inactivation of soybean lipoxygenase by acid pH was investigated by grinding whole soybeans in water acidified with HCl. The enzyme was found to be completely and irreversibly inactivated at pH 3.0 and below. From a study of enzyme kinetics of lipoxygenase extracted from the acidified soy slurries, significant changes were observed with the values of the Michaelis constant and in the enzyme inhibition patterns when the enzyme was exposed to pH of about 4.6 and below. This suggests a change in the conformation of lipoxygenase below this pH limit. A separate study using a purified lipoxygenase-1 supported the evidence that the enzyme was stable when preincubated between pH 3.0 and 9.0 but lost all of its activity when exposed to pH 3.0 and below. The purified enzyme also obeyed Michaelis-Menten kinetics at pH 5.6 to 9.2. A Dixon plot suggested a histidine residue to be the active site in the enzyme for the hydroperoxidation reaction.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Food Science

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Ali, Asbi Bin

• Agriculture, Food Science and Technology

Identifier

(UMI)AAI8908607

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70105