Polyphenol oxidase from wheat bran is a serpin

Area of Science:

• Biochemistry
• Enzymology
• Plant Science

Background:

• Polyphenol oxidase (PPO) enzymes are crucial in plant physiology.
• Understanding PPO function in cereals like wheat is important for agricultural applications.

Purpose of the Study:

• To isolate and characterize polyphenol oxidase (PPO) from wheat bran.
• To investigate the enzymatic properties and potential biological roles of wheat bran PPO.

Main Methods:

• Purification using ammonium sulfate fractionation, DEAE-cellulofine, CM-cellulofine chromatography, isoelectric focusing, and membrane adsorption.
• Enzyme characterization including SDS-PAGE for molecular weight, isoelectric focusing for pI, and kinetic analysis (K(m) values).
• N-terminal amino acid sequencing and protease inhibition assays.

Main Results:

• Achieved 150-fold purification of PPO with 4.2% recovery.
• Determined PPO molecular weight (37,000 Da), isoelectric point (4.4), and K(m) values for various substrates.
• Identified N-terminal sequence homology with serpin and protein Z; demonstrated strong inhibition of trypsin activity.

Conclusions:

• Wheat bran PPO possesses significant protease inhibitor activity.
• The dual activity of PPO suggests a vital role in defending wheat against biotic stresses like diseases and pests.